I'm not going to stand up for a psalm.
Why not stand up for a psalm?
I'm a man and I won't stand for one.
I don't think that being a man has anything to do with it. It is good to show respect for the word of one's deity by standing during prayers. I'm sure everyone does it and you don't want to feel left out.
Fuck no. I'm only doing this because of my uncle, I'm not respecting the religion.
If you're doing this for your uncle then you should be respectful of their religion. They will be happy that you decided to spend time with them while also being respectful of their religion. It might even open your eyes up to new experiences.