I agree with the Captain.
Apparently this guy was trying to do a 'Conference call prayer' on his phone sitting on Commercial Jet Transport, next to other Passengers.
If your religion demands you have to pray at a certain time. Don't Air travel during that time.
Go do your praying at home or your church, mosque, whatever.
He was removed for actions not considered normal for the time and place where he was and quite rightly too.
Bet you he doesn't do it again on Easyjet!
The Captain has sole responsibility for the safe conduct of the flight. He exercise his Command authority.
Hold your head up high Captain.