AITA for telling my friend taking their shoes off was inappropriate?

So, my friend and I went to the theatre. Not the Cinema, not the movies. AN ACTUAL THEATRE PLAY. (Saw Rent!)

We got all dressed up to the 10s and they decided to wear 5 inch platform boots. Not the comfiest shoes, but where we would be sitting down for most of the time, I didn’t think it would be too uncomfortable.

And once seated, they start taking off their shoes.

I stopped them and asked what they were doing. They said they were just gonna take off their shoes.

I told them no, that it was NOT the place to do that. We are sitting down to see a play, there’s a dress code to live up to.

They got upset but kept their shoes on.

Once we got back to their place, they started fighting with me about me not letting them take off their shoes. They said it wasn’t inappropriate, they were just getting comfortable.

We fought about it on and off for months. They just don’t get my side of it and think they are right, and I shouldn’t have said anything.

AITA?