I AGREE WITH YOUR OFFICEMATE.
I see religion as a system of belief, whether or not it includes the belief in a god or a belief in some other doctrines or principles. In that sense, at least I can say that Freedom FOR (or OF) religion also includes Freedom FROM religion. It is freedom for/of religion because you are free to believe in anything you like, and free to ACT in accordance with what you believe in. It also includes freedom FROM religion because a person may have no religion or religious belief at all. In other words, freedom refers to both - FREEDOM TO BELIEVE and FREEDOM NOT TO BELIEVE.
OR Im thinking also that your officemate has studied constitutional law and encountered these two concepts. But in law, freedom FROM religion refers more to the state's attitude towards religion in general. Freedom FROM religion - because the state does not want to espouse any particular belief system, which is a usual characteristic of democratic states. It refers more of an attitude of tolerance, where all religions are allowed in a state for as long as these do not conflict with public interest.