In terms of number of deaths, the CCP killed 15-55m in the Great Leap Forward. In terms of mass murders of history, they killed a lot more than many actual genocides.
I joined facebook as my first job out of college. I didn't really have a plan and they offered the most money.
The good:
There is a huge breadth of stuff to work on and good internal mobility. Whatever WLB, "impact," etc that you want, you can probably find it at fb. Getting tired of working on groups? You can work on some VR project. The tooling is really good so you can spin up whatever you want without having to think about infrastructure too much. They treat engineers well.
The bad:
Morality for sure. Nobody's perfect, but facebook felt especially evil sometimes. Lying to regulators etc is seen as strategic. Not wanting to be outed as an fb employee is definitely true.
Might not be a bad move, think about where the equity will go in the next few years, etc. If you want to start a family and high compensation, it's certainly not a bad move. If you think about the larger picture of what you're doing, I'd think it over very carefully.