I agree with Suki, TC. Just tell him you don't think it's a good idea, thank him, and you've done the right thing.
I had a friend who was an anesthesiologist who was about to get arrested for theft of anesthesia (and other) drugs from the hopsital. The police gave him a heads-up as a respected hospital doctor so he could tell his family and tie up loose ends but instead he committed suicide.
I tell you that just as a warning that you (probably) don't need. Sometimes other people give us the Grace that can kill us. They cannot and do not understand the underpinnings of shame we carry as addicts.
I hope you find a more fitting profession, if you want to continue to work.