I hate sharing music with my best friend
Why not share music? Aren't they your best friend?
Because he doesn't deserve listening to my music taste
You shouldn't be a gatekeeper to what kind of music you listen to. He is your best friend so you need to share with him, he is more open to new things than the regular person because you're friends. You don't know if you give him his next favorite band, and you can go to shows together.
Don't come to me and say that, I don't listen to shitty music
Best friends are expected to share with one another. Just because you don't think you listen to bad music doesn't mean others agree. Music tastes are subjective and you should be willing to let others try out some of your favorites so they can possibly feel the same about your music that you do.