Definition: Given a real-life anecdote of a complex ethical situation, generate a suitable title that describes the main event/root cause of the situation. Imagine that the given text is a social media post, and you have to write the title of the post, so the users can decide to read the main text or not.
Input: Me (22m) and my boyfriend (23m) have been together for four years now, and for the first three and a half years of our relationship he and his mother never spoke. She had basically turned on him when he came out as gay, starting off with subtle insults and digs which came to blows and she kicked him out at 17 with nowhere to go. We were friends at this point, and all of my friends already knew I'm gay, so we got quite close and got together a couple of years later. After being kicked out, he didn't have any contact with his mother or step-father until last May, although his relationship with his father is still good. 

Anyway, last July his mother messaged him out of the blue with an apology, and it was pretty decent and seemed sincere, so he decided to start talking to her again. Slowly, they started building a relationship again and even though my boyfriend was nervous about it, I could tell he was really happy to have a relationship with his mother again and I was excited for him. It came out a week or so later that she has cancer, but they caught it early and she is in treatment.

Her birthday was in September last year, and she invited my boyfriend out to her birthday meal. I didn't go, mostly because she didn't mention me in the message and we didn't want to rock the boat. They had a great time and started meeting up every couple of weeks.

I met her just before Christmas on a shopping trip with my boyfriend and his sister, and everything was good. She seemed really nice, and honestly everything seemed fine. Fast forward to Christmas Day. We spent the morning together, went to my parents' house for Christmas lunch and then to his parents' in the evening for a late dinner. I offered to help with the dishes after dinner, so it was me and his mother alone in the kitchen. Everything was fine albeit a little awkward, but then she started making little comments like "you don't look gay" (I'm a 6'4 firefighter with tattoos, quite typically manly I guess), and I laughed it off, but they started getting worse. The comments continued over the next few times I saw her (day after boxing day, NYD and yesterday), here's a list of some of them from all the occasions:

\- "don't you think you'd be better off with a woman than my son?" (he's a very feminine guy and I can tell she has a problem with that)

\- "I don't have a problem with you being gay but I wouldn't leave you around my kids" (she laughed at this one but I still think it's really offensive?)

\- uses "fag", "queer" and "homo" a lot

\- "a man like you shouldn't be taking it up the ass"

\- "I think it's disgusting but you do you"

\- "the idea of you kissing my son makes me sick"

\- "I hope he'll come to his senses and man up before you have the chance to get married"

\- "if I die with fags around my bed I'll never rest in peace"

A lot of the times she laughs off these comments like they're jokes, but I know if she said them when my boyfriend could hear he would be devastated, because she obviously hasn't changed her ways. There's been a few times she's made these comments (especially the slurs) around her husband and his son (but not my boyfriend) and it's obvious they are uncomfortable. I mentioned to her on NYD that she might want to cool it with the comments because I don't think my boyfriend would like them, and she said something along the lines of "he could do with hearing", so I don't think talking to her is an option, she clearly doesn't want to change.

My problem is, WIBTA if I told my boyfriend what's been happening and that I'm uncomfortable/upset with his mother, knowing it might cause tension  in - or even end - their relationship? I know that she's obviously the asshole, but I'm worried about being one too. 

potentially ruining my boyfriend's relationship with his mother