I don't support my brother's life choice
What choice do you not support?
He turned his back against me for choosing to be gay. I can't accept him anymore
I understand it's hard to see how people can experience basic urges like sexual preference so differently, but he didn't "betray" you with with his gayness, he is just expressing his sexual orientation as he feels compelled to.
I still don't like it, my brother shouldn't be into other guys.
You have no valid reason to not support your brother. Sexual preference is not a choice, you cannot shame him into changing his mind.