the look on his face is so perfect

Nonexistent. If you want it, find it yourself.

you can just say rainbow, you know

I love rainbows, but I'm not gay, who decided that they get to commandeer the rainbows?

Idk because the rainbow is a symbol of lgbt+ stuff now so naturally someone's going to associate it thusly? In this case, think Instagrams old colors made more sense in the context of this picture.

the lgbt flag is rainbow