Its called freedom of speech AOG, and it isn't harming anyone.
I don't know where you live but I am betting that it isn't Brighton. What difference does it make to you if some people want to celebrate and have a good time ? Attendance at Pride marches isn't compulsory....if you don't want your sensitive nature to be offended, look the other way !
I am reminded of the joke, about an old lady that calls 999, and tells the Police that there is a man in the block of flats opposite, who is exposing himself in the window.
The Police duly rush over to her flat, and find her sitting on a chair by the window, trembling with fear. The Police look out of the window, up and down the street, but can't see anything amiss.
"Oh no" the old lady says, "you've got to stand on the chair ! "