Sounds more like relativism than nihilism. Relativism is extremely common in mainstream political and moral discourse, especially in mass media journalism. This often takes the form of "bothsidesism" or "false balance," particularly in political discourse. So often, the merits of any claim (about politics, morality, scientific facts, even very basic claims about well-documented events that happened very recently, etc.) are judged by nothing except how strongly people appear to believe in them.

You see this a lot on Hacker News too, like when the discussion touches anything related to moderation, community standards/guidelines, censorship, fact-checking, etc. A particularly popular viewpoint around here seems to be that the government (or sometimes, any powerful corporation) cannot possibly be allowed to be involved in determining the validity of any claim, particularly if that claim is controversial, i.e. there are prominent people on both sides who appear to feel strongly about the claim.

Many people can teach, but to do it successfully they must come from a place of respect and trust. If someone I know wants to teach me about their field of knowledge, that will be successful. If an anonymous stranger presents information with an attitude of "I think this will interest you as it interested me", that will be successful.

If an anonymous stranger comes to me with "Let me tell you that how you think is wrong" - yea, I don't think I'm going to buy that.

What's the difference between this and pointing out how someone's argument is flawed? i.e. "You said 'X therefore Y', but following that reasoning you could say 'X implies (obviously-wrong) Z'. X is not logically incompatible with !Y because..."

(Not that this is ever successful in places like Twitter.)

"Arguement is flawed" is still in the eyes of the poster. I certainly wouldn't just unthinkingly accept this sort of feedback, and the simple truth is that internet "sources" are rarely trustworthy beyond the writer opinion.

It is still a matter of trust. Approach me with respect and I'll consider your POF. Approach me with "Your reasoning process is flawed beyond your understanding" and really - who the heck are you? In the anonymity of the internet you could be anyone.

It’s more that “teach critical thinking” often just means “condescend to an internet stranger about how flawed their thought process is” which, even if their thinking is flawed, isn’t exactly a winning strategy for helping people See The Light and whatnot.