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.
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.