My brother-in-law [21/M] groped me [30/F] at a family gathering, and my husband [27/M] of 1 year won't do anything about it

I've never liked my brother-in-law. He's kind of sexist, makes lots of crude jokes, and generally is not pleasant to be around. I've also caught him ogling me whenever I'm wearing anything revealing (which I do a decent amount of the time).
My husband and I have been married for 10 months and dating for 2 years before that. He is a sweet guy, but he can be kind of a pushover. He has a hard time standing up to his family, boss, anyone, you name it. Most of the time, this hasn't been a big issue since we live far away from his family. But this weekend, they had a big family reunion that we visited for. Last night, we all got pretty drunk. I went outside for some fresh air, and he did a fake "stumble" and reached out and grabbed my breasts over my dress, and kept his hands on them for way too long until I pushed them off. He leered at me, winked, and went back inside. I didn't know how to react in the moment, but afterwards I called my husband and told him.
He refused to do anything! He said his brother is just like that, and there's nothing he can do. I am thinking about going to stay at a hotel for the next 3 days before our flight home because I don't want to be in the same house as either of them. How can I convince my husband that he needs to stand up to his brother?
tl;dr my brother-in-law groped me while drunk at a family gathering and my husband won't do anything about it.


Source.