You may find it fun to repeat yourself on things you've already been proved wrong on
Except they haven't yet been proved wrong. Yes, the things they bring up have already been proved wrong time and time again, but they personally were not aware of it.
I forget the exact details, but during the 2008 presidential election, I responded to a thread that I think was about Barack Obama's birth certificate being no business of ours, saying that if the constitution requires the president be a naturally born citizen, then for any presidential candidate, their birth certificate is our business. And the replies I got figuratively bit my head off. I did not know why my post elicited such anger, because at the time I did not know about the large group of people trying to get Obama disqualified on the grounds of his not being a naturally born citizen, and of their dismissal of his birth certificate, or whatever.
Like I said, I don't remember the exact details. But the point is, if I was a different person, then instead of trying to figure out why this hatred got directed towards me, I might've immediately sided with the "birthers" and ignored any future attempts at "proving" me wrong.
It may get annoying debunking the same myths again and again, but please remember that for the person bringing the myth to your attention, they may have just heard about it and are legitimately curious about why this thing they just heard about does not debunk AGW.