AITBA for ruining my brothers first relationship?

My brother is fourteen and recently got his first ever girlfriend. I was SO excited for him and did my best to be a supportive older sibling. About a week ago I actually met and started talking to his girlfriend, she is the sweetest girl and I absolutely adore her like a sister. It's important to know that she is a Latina girl and one day, while we were talking, she actually told me that is that her grandparents are immigrants and she is bisexual. I honestly don't care about either of those details, after all I'm not only a genderfluid lesbian but i am also very pro immigration. My brother on the other hand... is a different story. He is firmly planted on the right side of the political fence and has repeatedly told me that he will never refer to me as his "sibling" and that I'll "get over" my lesbianism. He also is completely and totally against immigration and says its his dream to work for ICE. I felt like I should probably warn his girlfriend that these were his views... so I did. She looked wildly uncomfortable after I told her and left shortly after. Come to find out a few days later she had broken up with my brother and when he asked why she said, "your sibling told me a few eye opening things." My brother screamed at me and told me that I was a jerk who had ruined his first relationship because I "couldn't take a joke." My parents told me I should've kept my mouth shut because it wasn't my place to share my brothers political views and I was in the wrong. Then I found out that his ex had been apart of his friend group before they went out and now his friend group is divided in half and I'm wondering if maybe I DID overstep my boundaries. So am I the bad apple?