I was listening to a recording of Randy Alcorn speaking on the issue of the persecuted church, and he suggested saying something like this concerning the subject of blasphemy when done in your presence:
"Excuse me, could I ask you something? Could I make a request? In light of the fact that Jesus Christ is my best friend, He is Lord, and I believe that with all my heart, I would ask that you not dishonor his name in my presence."
A few years ago, I did address this issue with a coworker with whom I spent most of my day. She was annoyed with me (which I think will likely happen no matter what is said), but I didn't address it nearly as eloquently or as thought out as Randy Alcorn presented it in the above paragraph. I appreciated his attention to the subject and the provocation to thought on the matter.