I think here's a huge difference between the reports on this thread of one off meetings where a celeb has been offhand and the genuinely nasty celebs wher people have worked with them for a time.
We all have off days and I know if I was out shopping/eating and someone asked me to drop everything to do something related to my work life I'd be pretty peeved about it too. You may think it would "only take 2 seconds" but soon everyone in the shop or bar is asking and they've lost their down time
Then of course there's the divas who want the attention and pretend not to! I was in a club where Antony Cotton was and needed to get past him to get to the bar. I said excuse me and he barked some nonsence about not doing autographs at me! I had to ask my friend who the eff he was because I didn't watch Corrie and it was prior to the Jungle stuff