The main issue here is that this isn't exactly a "scholarly" dispute, where uncertainty stems from the depth, complexity and scope of literature, or from the vastity of sources needed to make an assessment. Meaning that any, very basic, book should do the trick. A good introduction of the "fascist phenomenon" in Europe is given by R. Paxton - Anatomy of Fascism. Unfortunately, this is one of those subjects where one is unlikely to get lost, unless they kind of want to.

In other words - and this is, obviously speaking from my relative experience - those who purport for Fascism and Communism to be either identical or close enough in nature and origin to be surmisable under the same category, do it either because they are lying or because they make certain assumption on the nature of "the left", which are - albeit perfectly legitimate in principle - rather unserviceable and, indeed, work contrary to our understanding of the matter at hand.

I could, of course, maintain that the central and distinctive character of a criminal organization is the use of deadly weapons. If I hold such an assumption as absolutely fundamental - and such as to allow me to reject any other "contingent" circumstance - then no real counterpoint to my argument can be produced. But, I am then left with a theory which does not only run counter to most accepted definitions of criminal organization, but also forces me to accept that there is no fundamental distinction between...

Let's omit the many, rather insulting, examples one can conjure up.

Something that we can do, instead, in assessing the nature of a certain historical phenomenon is to examine how it appeared to its contemporaries, how it appered to its members, how it operated in so far as we know, how it continued to appear to those who came after it, how it evolved and possibly changed through time, how it adapted to mutating circumstances, etc. In doing so, one can get a quite precise idea of what was going on.

Depending on the scope of our analysis, some of these features may take a more prominent role. It seems unadvisable to divert our undertainding entirely from practical matters though. An examination of the practical evolution of a certain phenomenon is also of extreme importance to assess the relative weight of its formal and ideological components - if an organization, to return to our previous example, claims they are only using violence "for protection" or according to a precise set of regulations, do they? do they, most of the time? do they blatantly ignore those principles, when they deem necessary?

This is not an irrelevant distinction. As for Italian Fascism, one can almost immediately notice that - while its ideological opposition to "the Italian Bolsheviks" was very practically turned into action - any, supposed, opposition to "capital" was left for the largest part unexecuted. Fascism was relentless in its dismantling of socialist labor organizations, and of the organisms of the socialist party. It did nothing of the sort with any alleged intention of nationalization, capital expropriation and so on. Also, and to avoid excessive complexities, the fundamentals of "productivism" which were apparent in almost all small currents of fascism since its beginnings, certainly recognized that one nation can do without organized socialist workers - indeed, maintained that it could do much better without them - but not without its productive forces. Even when certain contributors, like De Ambris - who remained far away from any form of institutional fascism though - mentioned a "partial expropriation", it was always aimed at "unproductive capital", and, as long as the state remained "a poor adminsitrator", as the war had proved, thoughts of nationalization (except for the traditional, protectionist, state control of mining resources) were relegated in a distant future.

But - I fear - this kind of dispute on the precise contents of Fascism risks losing sight of the main issue, which is, instead, of the most manifest character. It does ultimately lead to the same conclusion, which I don't see any reason to dispute.

Hence, unless your friend provides a specific argument (and, if you have one, by all means feel free to ask further clarification), any kind of basic information tool may probably suffice, or sort the same effect.