In this case it's a tiny bit more subtle. The Vzla posters are highly, highly unrepresentative of Venezuelans: English-speaking people with Internet access are likely to be rich whites or expats, and highly ideologically or even financially motivated on top of that to post a ton and rant everywhere about socialism and Maduro. Dealing with people like that can be a serious pain, especially if you don't aim to have an open debate sub but rather be more along the lines of a discussion sub for a particular group where you don't have to constantly defend basic assertions. Both models of sub have their place.

Now, that being said, /r/socialism goes far beyond "we need to moderate out people constantly ranting about socialism because they're making it difficult to have a decent conversation" on the regular. We all know how ban-happy they are and how fucking idiotic (you are now banned from /r/socialism) some of their rules are. Banning an entire sub worth of people because a few of them are disruptive and annoying is overkill, the net is too broad to be really useful. It's one thing to tag and ban noted members of small brigade subs that start drama everywhere they go, it's quite another to mass ban like that.

Since Venezuela's government and socialism in general are quite unpopular in this sub, let me make a comparison: suppose there were a bunch of rich, English speaking Yemeni expats that wanted to rant about the evils of capitalism and America's essential support of the Saudi war in Yemen, which has reduced hundreds of thousands to starvation and has seen things like the triple tap strike of funerals. I'd understand their anger but if I ran a sub about capitalism I probably wouldn't want dozens of those people constantly ranting and posting on every thread either. That wouldn't mean banning Yemenis on sight but it would mean telling people to take it somewhere else if they were making the forum substantially less usuable.