Churches and Temples

Question

When it comes to Reform and Conservative temples, you have said that a person may not enter them at all, for any purpose whatsoever. You have even said that it is prohibited to utilize a facility that is owned by a non-Orthodox synagogue. With regard to churches, though, you allow attending meetings, provided they are not held in the "sanctuary". Can you explain why churches are treated more leniently than non-Orthodox synagogues?