I've seen it before -- it involves blaming basically all war and all deaths under market economies on capitalism and doing serious gymnastics on deaths under non-market economies of the "it wasn't real socialism!" sort.
Usually it's Western Capitalism vs Communist [Dictatorship] Regimes and the argument is entirely valid. If you're forced in to it it's not communism -- people won't in general follow an ideology that contradicts their natural propensity to greed and winning above others (pride), so it generally is not communism when you're talking about groups above a small town size.
I spend quite a bit of time thinking about how to transition from our widely oppressive capitalistic system to a more communistic one in a way to accommodates people's propensity towards greed and still maintain democratic freedoms to the greatest extent. It's something that in the long term might solve a lot of our overuse of resources.
> I spend quite a bit of time thinking about how to transition from our widely oppressive capitalistic system to a more communistic one
The problem, of course, is that without force they’re short lived, like volatile molecules exposed to air. All matter eventually retreats to its most stable form.
Of course, nothing stops like minded individuals from forming communist societies (communes), and they do sometimes. Even a small one doesn’t stay together long without force or a very strong binding identity, such as religion or family.
If you're going to play "it isn't real socialism," then you have to play "it isn't real capitalism." I'm pro-free market with an econ background, and I'll be the first to tell you that virtually nothing in Western "capitalism" is all that recognizable as something promoted by free market economists.