I've expereinced this countless times and it really pees me off.
One time recnetly I was standing in the aisle of a theatre having got their early, with the performers (who I was there to photograph) , worked out where the best place for me to stand would be, set up my camera, only for this arrogant young woman to come in the room at the last minute and literaly stand immediately in front of me as if I wasn't there
Me: Excuse me, can you move please you're in my way
Her: Sorry but I'm the photographer I need to be here
Me: What photographer? There aren't mean to be any photogaphers here without permission
Her: Welll I'm sorry but it's all been organised
Me: By who?
Her: The organisers
Me: who?
Her: Just let me get on with my work
So I stepped up to the organisers and got her kicked out of the venue. She was nothing to do with them. Cheeky mare.
I'm sure there are some great photographers but my experiences with them haven't been great and have nearly descended into brawling on a few occasions.