When did you know you were a "prominent ufologist"?
By responding with facts, evidence and witness testimony. The skeptics often ask perceptive questions that cause me to reevaluate a position. Often that strengthens the position and sometimes it reveals flaws in either my thinking or the evidence.
Criticism is a different matter. Most of the time I just ignore it, especially when it is directed at me personally. Sometimes I make a quick response. But what do you do when people insist you are a government agent, have no evidence of it and require me to prove that I am not. Seems to me that they should offer the evidence so that it can be evaluated and refuted.
This all comes down to what is said, how it is said and what evidence is offered. We all should look at the evidence to decide if it is enough to change an opinion on something.