The problem I see it as (and yes this is a broad generalisation and not indicative of every gay person out there, in fact many are not like this and all should be taken on an individual basis) is the types who make their orientation the entire basis of thier personality.
Now its been a long held belief of mine that the only difference between a homosexual person and a heterosexual one is who they are sexually attracted to, nothing more, and its a stance I stand by despite it landing me in hot water a number of times and labeling me as homophobic a few times too.
But thats just it, they are no different but if you try to say that to the select few who make thier orientation the entire basis of thier person they go off on one.
I have no problem with people being gay, or with people being proud of being gay, all the more power to them but you are a person right? an individual? surely you have interests, hobbies, opinions, thoughts, feelings... a personality, not just an orientation
But sadly for those who do make thier orientation thier personality in that sense, and thus the majority you find at gay pride events (lets face it if your orentation is your personality as it is for some, this sort of event is going to be right up your alley) are the source of the majority of the bitchyness and arrogance that seems to come across
A little mock conversation to try and make my point that little clearer:
Me : hi
Gay Person : I'm Gay!
Me : thats great, good for you, so how are you?
Gay Person : I'm Gay!
Me : erm ok, you just said that, but hows life?
Gay Person : I'm Gay!
Me : Yeah I get it, hows your day going?
Gay Person : I'm Gay!
Me : Stop saying that already!
Gay Person : OMG thats so discriminatory and homophobic!!!
Me : *sigh*
sadly enough while I did just make that up on the spot I've had conversations that have gone very similar to that in the past