Social anonymity does not account for the fact that if the general consensus among a given population is "if you try to force me to do something, I'll defend myself" it very much lessens the impact a sociopath could have, as they would have to use means that, ultimately, aren't even immoral. We might all decry high-pressure salesmanship or quid pro quo, but there's nothing inherently immoral about either of these personal practices. Compare this to the men and women who comprise the state, who can use coercion to gain compliance and socialize the cost of doing so. Ostracism still works, boss.
So I understand a little where you're coming from, though your premise in the linked post is flawed (just like not all states are equally bad, not all ideologies are equal). Since not all ideologies are created equal, it is extremely helpful to sort out those that believe things diametrically opposed to reality and who can't universalize their ethics, as those are people who are going to waste your time. Aside from the fact they're provably wrong in their assertions, they're going to spend most (if not all) of their time with you trying to prove you wrong.
It's one thing to embrace an ideology and be completely uninformed. Happens across the spectrum. But you shouldn't welcome everyone with open arms. I'm not going to work together with communists, even if we happen to have crossed purposes in the moment. They can do their thing, and I'll do mine. If that ends up helping us separately, cool. They're still hopelessly backwards in their thinking and should rightly be considered an enemy to humanity.