His racist tweets were absolutely abhorrent. I don't give a flying fuck what the woman allegedly did to him, that does not give him a pass. If she assaulted him, well, there's a remedy for that which doesn't involve racist, sexist trash talk. I'd be pissed if someone assaulted me, but the filth he spouted would not even enter my brain.
If you have a job interacting with the public and you make reprehensible public statements which reflect badly on your employer, they have every right to fire your ass. I give Sirius XM credit for canning him. This isn't the first time his mouth has gotten him in trouble - he just miscalculated the reach of social media and how much damage he could inflict. Fuck him. Maybe Rush Limbaugh needs a sidekick.