I think that a Nations Government has an obligation to protect its society.
That would include making certain that wholesome family units have a place to live and thrive.
The WTBTS has a proven track record of completely shattering hundreds of thousands of once wholesome family units, so yes, to protect society the WTBTS should be banned.
For proof just google this: "family destroyed by Jehovah's Witnesses":
About 600,000 results (0.38 seconds) and thats a google search in the English Language only!
Matthew 7:15-20
"Be on the watch for the false prophets that come to YOU in sheep’s covering, but inside they are ravenous wolves. 16 By their fruits YOU will recognize them. Never do people gather grapes from thorns or figs from thistles, do they? 17 Likewise every good tree produces fine fruit, but every rotten tree produces worthless fruit; 18 a good tree cannot bear worthless fruit, neither can a rotten tree produce fine fruit. 19 Every tree not producing fine fruit gets cut down and thrown into the fire. 20 Really, then, by their fruits YOU will recognize those [men].
abe