Asklemmy

The closest thing you'll get to a list is the lists of slurs on Wikipedia because it's an everchanging list with different degrees and specific requirements for each phrase, for example Europe still considers it not rude to say the R word. It would be impossible to make a full list.

I tried to look but the most official one (from University of Washington) is kind of ridiculous. Following for better ideas.

One that a lot of people don't know about is 'jip/gyp', meaning to swindle or cheat. It's (most likely) derived from 'Gypsy' in reference to stereotypes about them being untrustworthy cheats.

Funnily enough, Gypsy itself actually derives from a mistaken medieval belief that the Gypsies, generally better called the Romani, originally come from Egypt. They're actually originally from India.

Considering this is a term related to animals, it is not particularly offensive. Or at least not the way you think it might be. While there are some phrases that are obviously offensive, pretty much any phrase, regardless how innocent, there will be someone who could construed it as offensive. I doubt this fellow considered it anything but that of work animals.

For years I used the term "shylock" as a pejorative for greedy people while being ignorant of the connotations of using the characters name that way. I didn't even know it was from a Shakespeare play.