Re: So i am met…
Not offending him, talk to him . lay it all out to him, that with the beleif he has, he isnt considered a muslim and what he needs to do and tell him all the facts and evidences. making sure that your satisfied that you ve told him everything that there is to knw in this sittuation.
Now its upto him to take the new path or continue being prosecuted.
This way he will be aware what the true faith is, you wont be Forcing anything onto him and most of All your Haq will be Fulfilled by guiding him to the right way. and if end of the day he doesnt agree with you. then he himself has to answer for what ever he chooses to follow.
just something to mention. If you knw that you can change someone or tell em without offending them, and you believ that it you will be helping someone.. then there is NO harm in trying is there. 
Plus end of the day you wont be left in a dilemma as what you can do or cant .. this way you would be trying and Maybe with a Possitive discussion and a convincing evidences … It may Change the guys life.
So Good Luck.