Sorry your situation is not at all funny, but the audacity of asking your sister to apologize to him after that is nuts. If he wanted to be a ‘whole family’ and be welcomed by your sister then he needs to acknowledge his faults and make amends. There are medications that can induce or enhance rage, but ultimate responsibility still lies with the person taking it. If medication or alcohol was pushing him towards hurting his loved ones, he needed to stop taking it or remove himself from places he could do harm while on it. Simple as.

Now for the flip-side of this situation, if your uncle is struggling with addiction and violence then quite likely he is in need of help himself. That is not said to excuse him, but simply to remind you and your sister that a part of addiction is physical dependence and part is mental dependence. You are not responsible or required to assist in his recovery, but if he means a great deal to you or if you feel he has improved enough to be safe to be around I’m sure it wouldn’t hurt. Don’t put yourself or your future in danger for that, but if you are open to it when you are an adult yourself supporting loved ones can be a part of a healthy recovery.

Having family with these issues is really difficult and if you need to talk to someone directly you should reach out to someone who is qualified to help you. I can’t promise doing so will make the situation better, but it is an option you should consider. I grew up in a household with substance use and physical violence, and escaped but not fully unscathed. It can be a long road to recovery both for those struggling with addicition and for those who survive the abuse that can come from someone struggling like that. Key takeaways from the work I’ve done in my own situation are the following:

• Don’t take blame for things other people have done. Any actions your uncle takes in response to arguments, or interactions with you are his to own. That includes if you fully cut off contact. What he does after that is on him.

• Your uncle is human and wasn’t always this way, and perhaps won’t always be this way. There is potential to help him grow and to get closer to him in the future, but as a child especially you do not have an obligation to help.

• You and the people around your uncle have likely picked up behaviors you are not even aware of to protect yourself around him. People build habits all the time without realizing, and the habits that may serve you now might become problems later in your life. Myself I became aggressively argumentive for a time when I felt like I was being attacked verbally, because that was a way that helped me as a child escape dangerous situations with my family. So later in life I would sometimes inappropriately lash out verbally in conversations that brought me back to that place, which harmed my relationships. The thing you have to remember is not to harbor too much guilt about what you do in the next few years to survive an unpleasant family dynamic. You are both children and shouldn’t have to be in this situation. You will do what you have to in order to get through. Be gentle with yourself after, you will recover faster if you understand that.

• The transphobic and misogynist things your uncle is saying are an unfortunately common and poisonously hateful ideology. Much like addiction it is possible to pull people out of it, but also like addiction there will be forces in your uncle’s life that brought him here. Likely in this case, a predatory class of media grifters who have filled his head with hate. Again it is not your responsibility as children to fix this. More than that, with this pushing him could make him fall further into it. He may still be actively making it worse by consuming conservative media as well. They also have an outsized presence in the addiction recovery space. So be ready for that

TLDR: NTA. Ineligible to even possibly be TA in this circumstance, and good luck and best wishes to you and your sister

Edit: Replaced an offer with a more appropriate response