He should.
Here's one of his followers: Mansoor Miah
Actually the comparison has some merit.
Choudary advocates a jihad of violent murder and terrorism.
Mandela’s role as a militant in the ANC and his proxy support (through his wife Winnie) of torturous murder (necklacing) of any who opposed them certainly qualifies him as a terrorist.
Now the comparison does not fit so well with Gandhi, who was a committed advocate of non-violence. But then he did have one thing in common with Moslems - the sleeping with young girls .....
Gandhi claimed that he strengthened himself by resisting temptation while doing this. I wonder however if he might not have been even stronger had he not done it at all. And of course the Moslems probably identify with Gandhi through the whole urine drinking thing.
(But no - Seriously folks - Choudary and Gandhi ... not too much in common.)