You don't think it's legitimately possible for someone to take pride in their ethnic heritage if they define said heritage as "white"? Due to history and current culture, it is highly unlikely that persons doing so at this time and place would not be racists, yes; but that's not inherently always true. In a hundred or two hundred years, perhaps "white" will be a minority, and given to non-racist expressions of ethnic pride or something.
The point was I trying to make is that you can't always judge statements like that on the surface, you have to be aware of the culture you are in. If it's a minority expressing pride, it may be a simple expression of support of whatever it is, or it may be an implied condemnation of whatever it isn't. Likewise if it's a majority making the same statement about itself...but history seems to demonstrate that when a majority feels the need to express such statements about itself, it does so more to exert its perceived superiority over the minority than as a simple expression of "pride".
"Straight Pride" might mean "it's good to be straight!", or it might mean "it's better to be straight". In the context of this culture, at this time, which seems more likely? Straights are the vast majority, it seems unlikely they would feel the need to express messages of support and solidarity for their condition in an effort to elicit sympathy and better treatment from others.