Not totally true. Title VII of the Civil Rights Act of 1964 protects religious speech from interfering in the employee/employer relationship. Just as homosexuality and race are protected classes in employment so is religion. Phil could plausibly argue that A&E terminated him because of his religious beliefs and his speaking about them.
Personally, I think an employer should be able to hire and fire anyone they please for whatever reason or no reason but that is not the law.
Thanks. I was only referring to the 1st Amendment, but the Act you just referenced certainly has bearing on this particular case, due to Phil's statement being overtly tied to his religious beliefs.