Am I being unreasonable?

My ex husband and I have been divorced for almost 4 years. We did not have a good marriage and it ended badly. It's been very challenging since. He does not show me any respect and is fighting with me any chance he can.

My mom, who I have a very good relationship with, continues to be nice to him, sit with him at our children's games when I'm not there and today she told me she bought him a father's day gift for the kids to give him.

This feels like a stab in the back and incredibly disrespectful because of how he treats me.

Am I being unreasonable by bringing this to her attention?