Okay, just before you read this, I'm not trying to be rude or anything. Just explaining stuff.
There is no religion, at least that I know of, that states being straight is an abomination. There is no such thing, as 'coming out' as straight. If you are straight, you rarely have reason to hide. The word 'straight' is not tossed around as an insult. It's not something people will single you out for, disown their child for, break relationships for. Do you realize, that at the end of every almost every LGBTQ+ parade, there are at least a couple of protesters screaming about the sins and wrongness of having a sexuality that's different from the norm?
It's pride month. People are celebrating part of their identity, not only accepting others but also themselves. The parade represents the community and their pride of it. Because there are many people out there who spit upon such. A pride parade probably would not be as common, nor necessary, if people weren't shunned and taught that not being straight was a sin.
Of course, you have a point. You're allowed to state your opinion. It's not illegal to proudly say you're straight. But people aren't bullying you for your sexuality, are they? The parade represents and symbolizes an idea of acceptance, that is needed for the community.
i also wanna add that 'straight pride' is just a thinly veiled cover for homophobia and also the same ppl behind it are also part of white supremacist circles. there may be nothing wrong with being straight, but there's no reason to have a parade for it because it was never taken away from you