I am looking for advice on confronting my mother who is sharing anti-gay posts on Facebook.

So essentially my mother's Facebook feed has been bothering me for a long time. I was always trying to reason my way out of confronting her. Now it is time to call a spade a spade and tell her I am not going to stand for it; and there is no place for people in my life who promote hate. The main reason I am so worried is that I am her only son; her mind is hanging on by a thread after my brother died. I am scared of tipping her mind to the deep end essentially where she can't come back from. The words 'disown' has come up in my head a lot. My girlfriend was very supportive and has reasoned a lot of things out with me. I wanted to get a broad take on how I should go about confronting her.