Should I go to a brother's wedding when I don't support the marriage?

So very long story short, my BIL is getting married next summer. Basically, he's engaged to this girl who from the beginning lied about her age (he was 21 she was 16 and said she was 20) and sent multiple other red flags including trashing his family and threatening his older brother. They also have completely different beliefs than the whole rest of the family. They've also threatened to not make his other 2 brothers groomsman. There's so much more toxicity to this, but bottom line is; should we go to a wedding we don't support? We don't plan to even bring our kids around them in the future because our belief systems are so wildly different and this girl has threatened basically everyone in the family.