Earlier quoted context omitted.
> but not okay for employees to band together to get paid what they're worth? Does not Facebook also retain the right to hire employees willing to take less?
That's why we need to fight right to work laws. If the entire staff is unionized and ready to fight, facebook can't just hire outside staff. Too much knowledge. Also the historical union attitude towards scab labour is another way to prevent this.
You mean violence? This is one of the reasons many people don't like unions.