To me, there's something kind of pointless about this because who is actually going to admit that they're entitled?

I'm not accusing you of anything, but anyone who does act with an entitled attitude toward a performer is not going to SEE that they are.
And I agree with what Fantabulous said -- it's hard to say stopping him on the street is a better approach than asking at the stage door, because even though the stage door is crazy, at least that's a time and a place kind of... reserved FOR those sorts of things. Of course, I understand he wasn't taking pictures at the stage door, so...

I wouldn't go so far as to say that it's wrong across the boards to ask for anything at places other than the stage door -- I think it depends on the person, the situation, and lots of specific factors.
see, I'm the kind of person who would be debating in my head whether or not to ask him, and by the time I decided, the light would have already changed and I'd be out of luck lol I am definitely that person. Not even about asking for pictures and stuff, but about approaching them in general. "Should I? Should I not? ... oh wait, they're gone."
A work of art is an invitation to love.