Confronting Parental Favoritism

When user a 27 male was 3, his parents (51m and 49f) adopted his newborn sister anny. She is deaf, and learned to lead lips incredibly well. She also got better grades and had more friends (I had a few while she was very social despite her disabilities) than me as a child, and my parents always called her the "best gift they could've asked for". They favored her, and gave her everything she asked for. They both made a lot of money, and sent her to a very nice private school, while I went to a weakly-funded public school two blocks from my house. When I was 11, I was made fun of and bullied by a kid in my class, and my father told me to toughen up. I went to my a teacher (who filed a report to the principal, who didn't do much) later, and my father called me weak for going to my teacher about a bully. The birthday parties for me were not really parties, but where I asked them to make my favorite dinner and they reluctantly agreed. My sister received massive parties, where my parents typically got her around 10 expensive gifts on top of everything else. They funded her college education in full, while they had told me to make do with the tiny bits of money they gave me for chores that I had been saving. More recently, they have asked me straight to my face why I wasn't as intelligent, social, and successful as my sister (mind you I make 20k more than her with no degree). Recently, she got engaged to a guy, who I'm currently good friends with and even learned sign language for my sister early in their relationship. They held a dinner party, where they openly talked about how they wish they had another golden child like my sister. They then asked me why I couldn't be like her. I got up, and asked to talk to them outside. I told them that they were neglectful assholes who never cared about me, and that they were bad parents. I then argued with them further, and they said that they were simply trying to make her feel better about her disability. By the end of the argument, they admitted they never wanted a son, and always wanted a child that would impress people and who would make them look good. I left angrily, and told my best friend about it, who said that it was good that I stranded up to them. However, the rest of my family (excluding my sister) believed that I was an ungrateful, whiny bitch who never appreciated what I had (of course this is after years of my parents telling them lies and after they told them a twisted version of the conversation).