I can see where you're coming from. I think you might be conflating the idea of what I consider worth taking the effort to block a Lemmy user over with what I might personally consider good ideas or opinions of inherent value. If I see a single post spewing genocidal rhetoric I'm not going to block the user and think that my blocking them is somehow going to make a difference in the underlying issue. I might want to see future the responses to their post (hopefully arguing against it), or I'll just scroll past it.
Now if I'm seeing that user consistently posting that same kind of thing as I browse around Lemmy, sure, I'll block them even if their posts are written in the most tactful and respectful way possible, because at that point it's become repetitive clutter that I don't want to constantly see while browsing Lemmy. The user blocking part comes in when something has become a consistent annoyance or frustration, because I find it's not worth the effort to block every user who posts something awful the first time I see it rather than just moving on.
Because you have primed yourself to ignore anyone who disagrees with you with any degree of vigour.
We might be experiencing some semantics issues. I don't equate angry or frustrated posts to inflammatory and trollish posts. I'm talking about when people are smugly trying to "own" or "dunk on" someone, or being excessively rude and accusatory (I can imagine some situations where this might sometimes be considered justified), or baiting a reaction trap. And I'm generalizing, not arguing a hard unbreakable rule. I agree there's nothing wrong with getting angry or frustrated about important issues that are a real problem, and I admit some of my most frustrating interactions have been with people who use the approach of "I'm being civil (in my argument for something awful, like genocidal rhetoric) and your angry response means I win the argument by default because I am being 'reasonable' while you are not." I really do get frustrated by that rhetoric playbook tactic. So I do think I see where you're coming from.
I do agree we've had different experiences, and that none are universal. I was caught in an "echo chamber" that almost had me voting in support of California's Proposition 8 (ban of same-sex marriage) back in the day and had I not been willing to listen to opposing views going against what I had been raised to believe in, I might still be trapped in that environment that I still see some of my old friends and family stuck in.
Boy, the trees are really sneezing today.