hbd chick's long essay Community Vs Communism has her usual thoroughness and wit. My own off-the-cuff thought was that socialism established itself in places that already had voluntary non-kin associations of support, such as Scandinavia; communism may be more of an attempt to shortcut the long slow development of such cultural supports by force.
However that socialism is limited to the nation only, and in those instances, the nation is essentially a tribe, an attenuated family where everyone looks like second cousins. You will note that those in even (now) socialist countries who don't look like second-cousins - gypsies, Jews, Saami - did not fare well in the 20th C. And the difficulties continue now, with different non-kin groups. The Great Tent of Sharing may only be able to remain erect so broadly given the current state of mankind.
It is good for us to try and be better, certainly, and a Christian thing to share more. Yet when things reach a certain stretch there seems to be a snapback response which may not be immediately visible but contains as much prejudice. I certainly see it in people who would cut their tongues out before they would make a racist or sexist comment, yet let drop amazing bigotries when speaking of their competitor cultures in America. Or also, who show off their superior morality by skipping over natural categories of caritas to visibly and obviously show that they love the unlovable more than you do. CS Lewis wrote of this in Screwtape, of Christians who would make a show of forgiving Hitler while acting spitefully to the circle of friends and relatives they actually encounter every day.
With such snapbacks, the net result is more strife and hatred in the world, not less, because the hatred is invisible to the hater. The unforgivable sin, I think, is the one that cannot be confessed, because we have become so hardened in our own conscience that we cannot see it.