Let me make sense for you then.
Step 1>>>> LGBT(and the whole rest of the alphabet) people are persecuted for nothing more than being who they are. The motives can vary, but, in all of them, the very EXISTENCE of these people is a menace and they should be purged. purged how? Killed, stashed away, "cured", etc.
Step 2>>>> When your very existence is targeted, it makes so that the very act of living be an act of resistance. If this is a hard concept for you to grasp, I suggest dropping twitter and reading papers on sociology, antropology, psychology, etc. This isn't some "random bs that people say because it sounds cool". There are tons and tons of debates around these themes in order to achieve these conclusions.
Step 3>>>> It doesn't work just for the LGBT community, but for all other social minorities who are historically persecuted in any given period of History. The "PRIDE" comes from striving to survive in a hostile world that wants to fuck you up purely because of something you have no control over. Your identity.
Step 4>>>> That's why its completely fucking retarded and moronic when people claim some dumb shit like "white pride" or "straight people pride", for these social groups are not historically persecuted. In fact, they are the persecutors.
There you go.
A step by step on why "gay pride" is a thing, but "straight pride" is just cope.