Im guessing you friend still believes in the bible. If they do show them John 6:19-23
19) “Sir,” the woman said, “I can see that you are a prophet. 20) Our ancestors worshiped on this mountain, but you Jews claim that the place where we must worship is in Jerusalem.”
21) “Woman,” Jesus replied, “believe me, a time is coming when you will worship the Father neither on this mountain nor in Jerusalem. 22 ....23 ) Yet a time is coming and has now come when the true worshipers will worship the Father in the Spirit and in truth, for they are the kind of worshipers the Father seeks."
So are we required to worship at a temple or kingdom hall? Nope.
What about 'not forsaking the gathering of ourselves together' card the b0rg likes to pull out? Show your friend Matt. 18:20.
Game over, the watchtower cult loses again.