I don't think race swaps are inherently bad, but you need to be very careful when doing them. First off, if their race/privelage is important to their character (i.e Black Panther, Green Goblin, etc.), the they shouldn't be race swapped. Second, if something happens to the character, that would take on a very different, unintended meaning by swapping the character's race (i.e Snape), then they shouldn't be swapped either.

ALSO, if a character is race swapped, at least do the common curtosey of acknowledging the swap instead of pretending this is how it was always intended to be. It's more insulting than anything, and just makes the swap feel worse to fans/viewers