Why do I get blocked when I try to defend my friends against trolls? Why does SW allow people to misuse and abuse the block feature like that?

We can't have vigilantes on Similar Worlds!
BTW we all get blocked sometimes it's for a reason, sometimes it's because the guy on the other end disagrees with being called out over something, or a multitude of other reasons. You didn't want to talk to that person anyway and whoever you were defending can block them if they don't like how the conversation goes.