"Straight pride" wouldn't necessarily be a problem if it were posted in a vacuum, but it has never once been posted except as a response to LGBT pride, exclusively by people who at best wouldn't be upset if the SC allowed states to ban gay marriage again.

Even if it weren't a problem, you should not be proud of whatever you want for no reason. Gay pride isn't about being proud of being gay, it's about being proud of being an exception to the default. They aren't proud of themselves because they have a sexuality, they're proud of themselves for putting up with a world where their sexuality paints a target on their back.