In short tell him to fuck off.

More detailed answer one, he is not you. Two, developing your own voice and style requires you to, (not be in rhythm, use wrong chord and fucking play differently than him.)

And if he's criticizing you for 'doing it wrong' tell him I want to do it that way and you could give to shits about his fucking opinion. Tell him, keep it to himself, he's not your parent, your teacher or your fucking mom.

FInally tell the little bitch to put on headphones if he can't control his grade school outbursts.

You have a right and hell a responsibility to be exactly where you are at and enjoy the journey. Not mentally fucked by some insecure controlling bitch trying to project himself onto you.

Fuck that noise.

You have a right, dare I say a responsibility to freely learn your way and in your time.