I'm going to shun my older brother
How come you feel like shunning someone you are supposed to be related to?
He pretended to be a feminist and treated me like a girl.
You resented being treated too much like the opposite sex when it came to your older brother, but this isn't so bad after all. Can you just be open and tell him to stop treating you this way, and prove to him how manly you really are? I think shunning a relative is just going to be wrong, you might need him one day for help.
You are so brainwashed by society. I am emasculated and this hurts my masculinity. I want to prove to my brother that his views are toxic and wrong.
Honesty is the best policy. If you feel inadequate it may help to talk with a therapist or join a team sport. Men are capable of being manly at whatever they do, don't let other people judge or label you.