I would imagine that with a group culture both of these would happen ^ because you all are so interconnected.

Can you try to stand up for yourself without trying to convince them, however? It is possible to stand up for yourself quietly by ignoring people and leaving their presence for the moment. Basically it is not rewarding their behavior with your presence. You actually don't even have to say anything.

I was playing with a 3 year old once and we didn't speak the same language. He was on my lap and then he started misbehaving. We were playing with blocks. I quietly put him down and started to put the blocks away. He tried to stop me and was making a fuss. After about ten seconds I stopped putting the blocks away and picked him back up and put him on my lap. He immediately started acting correctly. Of course my basic message to him was that I was not going to reward his misbehavior and he got the message very well (and I didn't say a word to him). Can you see how this could work with your family?

It seems like the way that you are doing it now is that you are trying to use your power to force your family into different behavior. This won't work.