Our pbass typically get along with everyone they can't eat! They're super chill except maybe with each other and even then they seem to be able to establish a suitable pecking order without anyone getting hurt.
It totally sucks to get a new fish that you're excited about and then not be able to keep them. It also sucks to trade your fish into your LFS for crappy credit and then go back and see how much they're trying to get out of him! Definitely been there! Sorry it didn't work out for you!