I'm going to insult my boyfriend's entire family
What do you have against his family?
Every time I'm over there I feel like they are scolding me.
I understand why you would be upset but you shouldn't be rude to people even if they are rude to you.  It would lead to a bigger fight and your partner would be upset.
They are rich so they are not going to control their mouth. They are not innocent.
I know you have a lot of disdain toward your boyfriends family and want to get back at them. But doing this is not going to be good for you or your boyfriend in the long run. I would recommend you talk to your boyfriend and see what you can do to get his family to like you better.