Hitler and his racial theorists, like Gunther, had a sort of 'list' of race. At the top were 'aryans'. But there were sub types of Aryans, like Nordics, Dinarics, Mediterraneans, Alpines, etc. The French fall under one of those subtypes of Aryans and Germans are Nordics. Within that Aryan umbrella the Nordics are the top. But there were more categories, with the very bottom being composed of Romani, Jews, and blacks. Slavs were also ranked particularly low and were not part of the Aryan 'race'. So the French were treated better than the Slavs of Poland and the Ukraine because they were Aryan. Also the Nazis wished to remove the Slavs from Eastern Europe either through extermination or driving them out in order for Lebensraum to occur, which was the idea of colonizing of additional land the nation needs.

Keep in mind Hitler often switched things around in order to meet his changing ideology as well as his practical goals. Such as the Japanese, who were granted 'honorary aryan status' unlike other 'asiatics'.

I mean, the more you read about Nazi racial ideology you just can't help but laugh, it is truly farcical.

Sources:

Mein Kampf and Germans into Nazis

Aside from racialist thinking that categorized non-Jewish French as higher than Slavs, there were a series of measures instituted by the German command that actively encouraged the rough treatment of civilians by members of the Wehrmacht. The Barbarossa Decree issued to the troops outlined the guidelines, or more exactly, the lack of them, for treating Soviet civilians. The second component of the Barbarossa Decree in particular highlighted how little priority the military regarded atrocities and other crimes against civilians:

Treatment of criminal acts by members of the Wehrmacht or its retinue against native civilians: 1. For acts which members of the Wehrmacht or its retinue commit against enemy civilians, there is no compulsion to prosecute, even when the act represents at the same time a military crime or offense. 2. In judging such deeds it is to be considered in any proceedings that the collapse in the year 1918, the later period of suffering of the German people, and the battle against National Socialism with the movement’s countless sacrifices of blood are incontestably to be attributed to Bolshevik influence, and that no German has forgotten that. 3. The chairman of the court must therefore examine whether a disciplinary reprimand is appropriate or whether it is necessary to institute judicial proceedings. The chairman only orders court-martial proceedings for acts against native inhabitants, when the maintenance of discipline or the protection of the troops demands it. That applies, for example, in the case of serious acts that result from the loss of sexual restraint, are derived from a criminal disposition, or are a sign that the troops are threatening to run wild. Criminal acts, by which lodgings or supplies or other plunder are senselessly destroyed to the detriment of our own troops, are not on the whole to be judged more leniently.

In short, the Wehrmacht told its soldiers that any criminal act that did not contradict military operations or create discipline problems would not be punished. The Barbarossa Decrees coexisted with the Commissar Decrees, which exempted Germans from any adherence to standards of international law when dealing with Communist Party officials captured in uniform, and wider anti-partisan measures which prompted German troops to meet any civilian resistance with fire and sword. Chief of OKH's General Staff Franz Halder noted to himself in planning meetings for Barbarossa in March 1941 that the execution of commissars and other Communist Party officials was:

This is no job for military courts. The individual troop commanders must realize the issues at stake. They must be leaders in this fight. The troops must fight back with the methods with which they are attacked. Commissars and GPU men are criminals and must be dealt with as such. This need not mean that the troops should get out of hand. Rather, the commanders must give orders which express the common feeling of their men . . . Commanders must make the sacrifice of overcoming their personal scruples.

The Third Reich thus not only eliminated the mechanisms for controlling their troops' behavior, the planning and execution of Barbarossa actively discouraged any restraint on the part of their troops.

This lack of any controlling mechanism reenforced the ideological component of Germany's invasion. Although only a relatively small portion of the mainline army formations were members of the NSDAP, a large portion of the army had participated in National Socialist organizations like the Hitler Youth and Reichsarbeitsdienst (RAD). Furthermore, an important part of the vetting process for both officers and NCOs was an evaluation of their commitment to National Socialism. While these evaluations were not indicative of an individual's own beliefs, they show the extent to which ideology played a major role in the careers of these soldiers. A strong ideological commitment to this war of extermination actually increased higher up the chain of command. There were relatively few protests by line officers against both the Commissar Orders and the Barbarossa Decrees, and most of them were on the grounds of either pragmatism of ruling a conquered population or concern about the removal of the threat of court martial to enforce discipline. The Wehrmacht stepped up its propaganda efforts in the months prior to Barbarossa and during it, and these efforts often conflated both Communism and Judaism.

The case of Poland was roughly analogous to that of the Soviet Union. Like the USSR, in the Third Reich's mentality the geographic space "Poland" simply possessed no right exist. The Germans instead considered this geographical space as fundamentally German in origin and the clearing out of the Polish "steppe-culture" that had infested the land was a fundamental component of the regeneration of this Germanic space. Ethnic Poles either were to be Germanized or dispossessed. The problem for German occupation was there was no standard method of Germanization- there were a lot of theories as to how one could tell German from non-German such as eye-color or hair, but these methods were often junk science and seldom reflected reality. The SS sought to propagate the Deutsche Volksliste, a four-stage classification of the purportedly Germanic character and the ease which an individual could be Germanized, but the criteria used were highly subjective. Local authorities were to compel the population to register their racial classification and decide whether or not these individuals were being honest. The chaotic administration of these areas also created a lot of confusion and undermined the already tenuous logic of the Volksliste. Here the contrast between the new Polish Gaue Danzig-West Prussia and Wartheland is instructive. Berlin had decreed that these areas were to be Germanized as soon as possible, but did not give the heads of these regions any formal instructions as to how to do so. Albert Forster, the Gauleiter of Danzig-West Prussia saw this end objective and tried to accomplish it in the most expedient way possible by Germanization of whole communities by fiat. Poles that would accept Germanization, have rudimentary documentation of their German heritage, and also wealthy enough to pay bribes (Forster was notoriously corrupt) they would be Germanized. Of course, many Poles either were unable or unwilling to undergo this Germanization process and the Germanization of West-Danzig was quite fickle- prestige projects required more care at Germanizing than others. In contrast to Forster, Wartheland's Gauleiter Arthur Greiser was very much a true believer and was more systematic with the Germanization of his region. Greiser deported some six times more Poles than his rival Forster and was more serious about implementing the Volksliste classification. Greiser and Forster also hated each other and tried to use the others' actions to jockey for more power. Forster would present his shoddy Germanization as achieving results quickly in contrast to Wartheland's slower pace, but Greiser would contend his Danzig-West-Prussian rival was betraying the racialist principles of National Socialism. Himmler was sympathetic to Greiser, but Hitler sided more with Forster as the Gauleiter in Nazi political system had broad authority to act on local conditions. So long as there was no open resurgence of Polish culture and the Jews were deported, Forster's approach was palatable. Again, like the Wehrmacht's invasion of the USSR, there was no real mechanism to check abuses because extending protections to these conquered populations was antithetical to the Third Reich's war of conquest.

France, although a defeated power, lacked many of these conditions. Compared to Barbarossa, Fall Gelb had very little of an ideological rationale to it and the Wehrmacht retained elements of military justice. German occupation policy towards France were a series of expedient measures predicated upon squeezing the maximum amount of resources out of the country as possible. German soldiers were paid in Francs or their equivalents at a highly favorable rate of exchange. While German occupation was exploitative, German policy towards France never verged upon extermination.

Sources

Epstein, Catherine. Model Nazi: Arthur Greiser and the Occupation of Western Poland. Oxford: Oxford University Press, 2010.

Militärgeschichtliches Forschungsamt. Germany and the Second World War: Volume IV: The Attack upon the Soviet Union. Oxford: Clarendon Press, 1998.

_. Germany and the Second World War: Volume IX/I: German Wartime Society 1939-1945: Politicization, Disintegration, and the Struggle for Survival. Oxford: Clarendon Press, 1998.

_. Germany and the Second World War Volume IX/II German Wartime Society 1939-1945: Exploitation, Interpretations, Exclusion. Oxford: Clarendon Press, 1998.