Absolutely. Are you suggesting that a liberal employee should not be allowed to quit an anti-abortion company?
>Should A trump supporter be able to fire anyone in their company that supported Hillary?
Absolutely. Should a Hillary supporter not be allowed to quit a company that supported Trump?
>I remember when a few companies opposed supporting birth control and abortions and didn't want to pay for it through employee healthcare plans.
By law, all health insurance policies are required to provide this coverage. Those companies can still be vocally against abortion, but they still have to comply with the law. What if someone is religiously against traffic lights? Then their options are to follow the law or don't drive. Nothing to do with freedom of speech.