I'm not going to leave the room when my brother is masturbating.
Why would you do that?
I don't want to miss an impressive show. Watching masturbating has always been my favorite hobby.
It is extremely unacceptable to not give people privacy when they are doing certain things. If your brother wants you to leave the room when he does something like that, you should respect his wishes and give him some privacy.
He doesn't control me so I can do whatever I want.
It is weird that you want to see your brother masturbating. You really should give him privacy.