What would have been a good reply to guy that was mad at me for standing behind him on the bus??

This happened in a vile US ghetto area. All I did was stand, not sit, in the bus and look out window. Then, a guy turns out and asks me if I really need to stand over him?? idgaf about him. I was confused and replied with a What. He repeated and told me to sit down. I said no as knee pain. He tries to prove me wrong by saying that I got on the bus. I said it is only when sitting down. Then, he tells me I belong in a hospital, not on bus?? Then, he gets up and moves seat to front. During the rest of ride, he continues to watch me wtf. Idk if he was planning on stabbing me jfc. The entire thing is so strange, but is no surprise considering the unstable in my area.

Was there a better reply? It was so random. imo, he seems mental? No one has ever reacted that way to me standing in bus wtf. Another time, a guy told me to sit. I said no. He asked Why? I said I wanted steps and we just laughed lol.