So is it rude to put one's feet on the bulkhead wall? Does it make a difference whether one's shoes are on or off? Does it matter if the wall is carpeted or not?

I ask in part because I had my feet on the bulkhead wall of a UX Shuttle America 340 several months ago and was told by the FA that she was going to have to "wash [the plane's] walls" as a result of my feet being up there. I didn't want to argue, so I took my feet down, but I thought it was a bit picky (especially given how run-down the plane was already).