You think you are helping out the site and correcting a wrong answer.
Maybe you are finding a poster who consistently posts information that you know to be wrong. The thing to do is to correct them, and provide proof that their assumptions and answers are incorrect.
You are making the Internet better by correcting them and writing out answers with citations that prove your point. But it isn't working, and that poster isn't changing and now they are arguing with you in the comments, or rolling back your edits.
What to do if that person doesn't WANT your help or feedback?
See Also the Civility Requirement of our site.