Patrick has been wanting a child for awhile and make a decent income so that's not an issue, but has had a hard time with adoption because some people would take issue with him being a single parent, his identity or both. He finally got to adopt and bond with Buddy, a wolf/dog (likely pitbull) mix who had a hard time being adopted because of him being a hybrid.

And then Patrick's mother tried getting Social Services to take the adopted child away because she sees Patrick as to delusional to raise a child. (Thankfully this failed as social services could not find a sufficient reason to remove Buddy.)
Patrick's mother has never been accepting a Patrick's identity or the fact that he is bisexual. They had a pretty normal relationship before Patrick came out as bi and it when down hill from there. While on some level she never stopped caring, her prejudice views outweighed what is supposed to be unconditional love and the relationship became pretty toxic. For a long time Patrick did hope that his mother learn to be more accepting and they could have what they had together when he was young, but that sadly never happened.

Well pretty much a pacifist and able to not let most things get to him, this got to him. He is telling her to leave and cutting her out of his life as she went way to far. she's likely done things in the past were he should have cut her out sooner, but this was the braking point for him.