"Pride" in who you are seems to be looked down apon negatively in recent years, particularly in more liberal circles. To take an aspect of yourself that isn't universal and say you are proud to be it, seems to show the world you think you are "better" than others because of that aspect which is simply not true.
As you say though, it only really seems to apply to straight caucasians. That could be because of our past, lets face it we haven't been the most accepting of folks. At one point, not all that long ago, it was generally believed that to be white and straight was the best way to be and as a result we're seeing a backlash now where to feel pride in who we are means we should feel guilty.
I can see the later replies to this thread already stating "taking pride in skin colour, your country of birth etc is retarded and hopefully we as a species will move past this". Then in another thread they will actively support a gay pride march or black history month. Neither of those things I have a problem with by the way, as long as the ability to rise up and say "this is who I am" is universal. Otherwise, events which promote "minorities" in the western world do nothing but create divisions between themselves and the majority whom they desire to be equal with.
Pride is something to be celebrated, it's something we as humans cannot escape. The problem lies in that not everyone is proud for the same reason. The Royal Wedding was the most recent example of good pride and the few occassions I have seen that have been similar made me incredibly proud to be English. Regardless of Nationality, creed, sexuality, millions of people came together to celebrate our heritage and a focal point of British culture. Even with the "why should I care it's a dead institution" people bitching in the wings, it was still a beautiful day because it allowed everyone to come together and celebrate without restricting the celebrations to a specific group.
How many Americans here will be doing nothing or don't give two shits about July 4th? Or Thanksgiving? Those are days for all Americans, wherever their origins to celebrate and no one is left out. These are surely more good examples of how people can come together and show unity the right way?
Everyone deserves the right to celebrate who they are, where they are from, without being a dick about it to those outside of that group. I think that is where alot of "pro-white" groups fail, and "pro-black", "pro-islam" and most other pro-whatevers for that matter. How about having a pride day but making it more a community thing? The focal point could be islam, black history/culture, gay pride, white pride, but get the whole community included? Everyone could learn about each other that way without a feeling of "we're different and we want to shout about it" and instead create a feeling of "yeah we're different, but we want to share and celebrate that with everyone and when you have your day we'll come along to that too, parties all round!"
Ok, I've rambled enough and probably made little sense so I'll stop.