I don't think the artists who delude themselves in that way are the majority; most of us have thick enough skin to be candid about the reasons why we share our art. And like others have said, having other people see your work can be part of the fun in 'doing something for fun', and there's a difference between 'doing something for yourself only' and 'doing something for yourself FIRST'.
Me, I can illustrate both of those things: I am interested in fame and money, and I have been from day 1. I've gotten to a point where pretty much everything I draw has a potential audience in mind; those days of doodling stories in composition notebooks and throwing them into drawers are over.
But I've stated before that I am my most important audience member. What I like, in character design and plot construction, comes first. It's only after that that I worry about whether someone else will like it.
I think what pisses artists off is when certain audience members expect the reverse. Like, even if it's only a tiny little hint of entitlement, it can be really offensive when you feel you're hearing that what you like isn't good enough, and should be secondary to what Commenter A likes.
I've had to deal with people basically writing my entire plot for me in advance, as if I'd read their magical little comments and decide to use them as an outline for MY comic. It doesn't happen much anymore, but back when it did...well, let's just say I didn't have the patience to brush them all off as 'insensitive 10-year-olds'.
Every once it a while I'd go off and give someone the MAKE YOUR OWN DAMN COMIC speech, not because I couldn't handle the prospect of other people seeing and having opinions on my work, but just because I'd get fed up with people who figured their opinions were important enough to keep pushing on me. I've dealt with people who had the gall to check up on me and ask WHEN I was going to use the suggestion they gave last week or whatever. Not 'if', WHEN. It really gets to you after a while...
Was it wrong for me to get angry at those people, and maybe blow up at some of them?? I don't know...but all that is to say, don't judge a book by its cover, I guess. The artist that tells you DON'T LIKE IT DON'T READ may have spent the last few weeks dealing with readers far more entitled than you are; you may just have been unlucky enough to show up with a constructive criticism at the wrong time. =/