It’s unlikely that anyone will cause trouble at a Pride event, but if you see anyone being abusive towards participants, it’s your chance to step in (provided, of course, that you feel safe). Be respectful of the people who Pride is actually for, take a backseat and enjoy the atmosphere.
And because basically every other space that’s ever existed has been designed for, and occupied by, straight people.
Sure, this sounds harsh, but Pride events are safe spaces for LGBTQ people because the world has been (and often still is) a hostile place.