Try to ignore them if you can. Just be your own pleasant self and keep as much distance as you can. You only have to deal with them for a few hours a day (if that much) but they have to live with themselves for the rest of their lives.
One thing I would avoid: don’t talk negatively about them to anybody. If other people solicit your input, do not engage in a bashing in absentiam. I like to follow that rule that if you have nothing positive to say, say nothing at all.