BriseFlots

@JMac Singleing out person in the workplace and actively excluding them from social events outside of work may or may not be spinned into moral harassment / discrimination by lawyers. An appropriate way to deal with this could be to invite people in smaller groups (say invite 4 persons twice) so that the person is still excluded from the parties but is not singled out.

It's not because you get to decide who you invite to your party that it's appropriate to invite everyone but one person. These are two totally unrelated propositions.

@LightnessRacesinOrbit I totally agree with your comment. There is a difference between something being deserved / rude / legal / moral / appropriate, and this answers shows it clearly. Which is why this a better answer imo than the one made by Joe.

Lawyer up and try to see if you can sue them for damages.