I can't really tell you how communists think, to be honest, because I am not exactly one. It's a weird thing (in the US?) that everyone who is not libertarian is considered communist (and not any communist: mostly the kind that is "the enemy" in cold war era video games, apparently).

There are many systems that would probably be considered communist in the US (at least by those of you who seem to have no clue about anything that is not libertarian) that work really well without genocides. But you'd have to open a book that is not US-centered to see that.