I thought the same until I saw the reason for gay pride etc. There is still huge discrimination and violence against gay people and it's used as a way of combating that.
https://en.m.wikipedia.org/wiki/Gay_pride
People are moaning about it, when I moan about something it's painted as outrage. I don't understand why anyone would have a negative opinion of something that's just showing solidarity and being inclusive of a group that faces discrimination.