Get him to show you one scripture in the New Testament in the NWT that requires Christians to be Witnesses of Jehovah .
Their is not one .
Do a little research of your own about how many scriptures their are in the NT that require Christians to be witnesses of , for , or about Jesus Christ and their are at least 20 such scriptures .
Philippians 2:9 -10 God gave Jesus a name that is above every other name ( including the name Jehovah ) "so that in the name of Jesus every knee should bend ( in worship ) in those in heaven and those on earth and those under the ground "
An obvious reference that God wants Christians to worship Jesus to be able to come to him in this period of time as a test of their faith.