Dr Antony McRoy's been speaking to Premier after Mr Choudhary was convicted of terror offences, having encouraged people to join Islamic State - a banned organisation which has waged war on Britain.
There's been a call to review UK anti-terror laws since, because Mr Choudhary was able to preach radical Islam openly on social media and in public for years before he was finally arrested in 2014 when he openly pledged allegiance to Islamic State.
Mr McRoy, who has met Anjem Choudhary and some of the terrorists he has radicalised several times, has said Christians have "hidden" in their churches rather than confronting them.
He also claims that radical Islamist preachers are often unable to defend their views when they are subjected to extreme scrutiny.
Speaking on Premier's News Hour he said: "We've got to ask ourselves: how many people did confront him personally? How many Christians went up to him to take him on? How many Christians do this to his supporters?
"Rarely do I ever see anyone do that. We've hidden behind our walls in our churches.
"Just very recently I had to deal with one of them who was harassing some Christians, and I took him on and very easily I had him on the ropes very quickly."
Listen to Premier's Alex Williams speaking to Dr Antony McRoy on the News Hour:
