What everyone just said.
Be careful how you approach this. May come off more self righteous than anything else. In my experience, if you want to help influence someone you have to help them understand, and you need to be willing to put in a lot of time with this person instead of delivering the blow all at once. Don't get me wrong, it may work, but I doubt it.
Does this friend know about your beliefs? Instead of telling him he is wrong, maybe start by asking him what he thinks about his work. Ask if he likes his job. Always keep in mind that we are all along different points on this path. Perhaps your good friendship over the years will be enough of a positive influence that he will decide to stop his job on his own.