"You're gay"

I just need to get something off my chest - why is "you're gay" even considered an insult? I mean, for something to be an insult it actually has to be insulting, right? 
I don't really understand the use of this as an insult. I would consider someone saying "you're gay" as an insult on the same ground as someone saying to me "you like the colour pink" or "you have blonde hair", it's not something you can change. 

I understand that it has been derived from total homophobia, but we're supposed to live in an age where the majority of people are supposedly for gay rights, so, why are people still using the words "gay" and "f*g" as insults?

I would also like to know why the main argument for gay rights is "it's not a choice" (actually, if I'm asking questions, I'd like to know why there has to be an argument at all). I absolutely understand that it's not a choice, but even if it were, there is nothing wrong with loving someone, or wanting to love someone, of the same sex. I mean, "straight" people don't miraculously decide that they're going to be straight, so why would anyone decide to be gay, bisexual, queer, transgendered etc. 

Where do you even draw the line between straight, gay, queer etc.? Someone could consider themselves straight, but also view someone of the same sex "hot" or attractive, so would that immediately make them queer or bisexual? I don't know, but I don't think it's anyone's business if it's their life. 

I think if people of the LBGTQ community have to "come out", then shouldn't straight people have to as well? Shouldn't we all have to tell people "what" we are? 

I'm sick of society telling everyone they prove themselves or defend themselves for what they are. I'm tired of gay being used as an insult or a synonym for shitty. It's not. It's awesome to be gay, or straight, or queer, or transgendered, or bisexual, or anything if that's what you are.

There's nothing better than being you, and no one should ever have to apologise for that.

#unlesstheyreareallyshittyperson