I want to be sure you're referring to dive bombers in particular. They were not commonly used against tanks, the main dive bombers being the A36 Apache for the US and the Ju-87 (Stuka) for the Germans. Neither of which were particularly used against tanks or anything else in the later part of the war. However, given that the typical tank of the early war period had bugger-all armor, it is not inconceivable that Stukas could have been effective against them. In fairness, however, a Stuka/Hs.129 unit is credited with being the first unit to stop, by air power alone, an armoured attack, near Prokohovka, Kursk 1943.
The problem/myth comes when you start looking at allied ground attack aircraft. Unlike the Germans and Russians, the Americans and British didn't really use any purpose-built equipment. The P47s or Typhoons which have their reputation of destroying Panzers were really fighters re-roled for ground attack. As a result, although they made a lot of noise, and the pilots caim back with huge claims of kills against enemy tanks, research conducted on destroyed tanks indicates that their claims of practical effectiveness against tanks was hugely overstated. For example, Mortain had what was known as "The Day of the Typhoons". US and UK pilots claimed to have destroyed 77 tanks, with an additional 43 probable. The Operational Research Squadron, after looking at the wrecks, credited air power with 9.
That's not to say they didn't have huge psychological effect, or an effect against softer targets than tanks, but the idea of "Egads, an enemy Panther, let's call in an airstrike" is a bit misconceived. Of course, if the end result is that the enemy Panzer is no longer a problem (because it's out of gas, abandoned by crew or whatever), nobody on the ground is going to complain about the fact that it wasn't because the P47 actually punched a hole in it.
When it comes to dedicated ground attack aircraft such as the IL-2 or Hs.129, I have no reason to believe that they were not as effective against tanks as they are claimed to have been, but they were not dive bombers.
If you're referring to the "myth" of aircraft being highly effective tank-killers in World War II, the "when" is at the time, largely based on claims by pilots. All air claims were hard to verify and overstated, and small targets on the ground were particularly difficult to positively identify and judge the results of attacks against. Rigorous analysis of causes of tank knockouts was difficult, and not always undertaken or widely available, to be able to provide evidence for or against air claims.
Starting with the German invasion of France in 1940, for example, Stukas (and the Hs 123s of II.(Schlacht)/LG 2) were credited with defeating Allied tank attacks in instances such as Montcornet, Arras and Cambrai. Both German and Soviet aircraft claimed large numbers of tanks destroyed during the battle of Kursk in 1943, and Allied fighter-bombers over Normandy in 1944 also claimed large numbers of tanks including during the Mortain counterattack mentioned by /u/The_Chieftain_WG . Various contemporary and post-war accounts reflect such claims, e.g. of Mortain "The intervention of the Tactical Air Forces, especially the rocket-firing Typhoons, was decisive." (The Royal Air Force 1939-1945, Volume III: The Fight is Won).
The "myth-busting" is, as far as I'm aware, more recent, such as Brereton Greenhous in the 1980s, e.g. Aircraft vs Armor: Cambrai to Yom Kippur, Ian Gooderson in the 1990s on the Allied tactical air forces, Nigel Askey's [Combat Aircraft Versus Armour In WWII] (http://www.operationbarbarossa.net/combat-aircraft-versus-armour-in-wwii/) looking at Kursk and Normandy. These focus on the few cases of actually destroyed tanks that can be attributed to bombs and rockets to give a more accurate picture of air power, though as sometimes happens with myth-busting the scales can tip a bit far the other way (e.g. Askey's comparisons of German tank and Allied air losses aren't particularly relevant, as 2nd TAF engaged a far wider array of targets than tanks alone).
The more balanced works now take into account the difficulty aircraft had in actually destroying tanks, but the important work they performed in restricting movement, causing damage, hitting soft-skinned targets, and the psychological impact of air attack (e.g. Gooderson's entire thesis/book, Peter C. Smith on the Stukas at Montcornet: "Although direct hits on such targets as tanks were rare, the use of the new fragmentation bombs on theses occasions, which stripped the tracks from the tanks and rendered them inoperable, was critical.")