This is a problem area. Some harrassment is bad, but given most employees are at will and the harrassment is not prohibited by law (e.g., like sex discrimination, race discrimination, etc.) you are put in an awkward position. You need to talk to a Mo. Lawyer. At least in PA, the harrassment you complained about before the economy went south would probably get you Unemployment on the rationale you were forced to quit. In PA, I have found quit cases are much tougher now. I would only quit if a Mo. lawyer told me he felt I could more than likely get UC. In PA, I would advise the client to wait until manager went obviously over the line (hit you or cursed a blue streak at you). Withholding a pay check might be an avenue of redress for UC as repeat failures to pay in PA would be grounds to quit. Good luck!!!
Contact HIS supervisors. If he retaliates, he will be in much worse shape and so will be your company. His grabbing you sounds like an assault 3rd crime. If he keeps grabbing you, you can call the police as it is a crime to touch someone in an offensive or painful manner or to even cause apprehension by doing so (assault 3rd degree).
Start with his supervisors and complain about the possible criminal conduct. If discharged for reporting what you think is a criminal occurrene, you might have a claim for whistleblowing.
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If your pay is being withheld, you have a claim under federal wage and hour laws.
His grabbing you and shoving you is assault and battery. You would be able to sue GM for negligent supervision of their employees. If your supervisor has a track record of this, and was hired with that record, then you'd be able to assert negligent hiring.
If he is treating employees differently because of their race, sex, age, color, national origin, or religion then you definitely have a discrimination lawsuit. You need to report this to his superiors and get an attorney in your area.