In my headcanon, fluffies don’t know what our slurs or expletives mean. They react to the tone and manner in which they are said.
You can trick a fluffy into thinking they are good, endearing terms. You can scare a fluffy into thinking they’re mean, without them knowing why.
Feral fluffies wouldn’t care either way due to lack of human interaction, but a foal having a name when they can only call each other “fluffy” would be insulting to them.