There are lots of people who want airtime on a prime time news channel. Given that it's prime time, they should only be given airtime if their views are that of a significant number of people. They should NOT be given airtime if their views are that of a tiny number of people, especially if it's known that the tiny number of people is essentially a bunch of terrorists.
I think if he's given airtime, it's incumbent on the interviewer and channel to give him a grilling, and not simply allow him to ignore their line of questioning and spout off propaganda. If he doesn't answer the questions asked, he should not be broadcast. Instead, a message should be broadcast along the lines of "We did interview Mr Choudary, but he failed to answer the questions asked" (similar to the "declined to comment" we hear so often). For this reason, live interviews are to be avoided.
I trust our major news channels to determine whether or not he answered the questions asked in a way that was worth broadcasting. In this way it's those channels, and not he, who would ultimately be responsible for disseminating terrorist propaganda through their networks.
With the IRA, the fact that an actor had to voice their words meant that nothing got broadcast live and that allowed editorial decisions to be made.
It's the editorial decision-making that's the key component of a workable approach that allows free speech within limits.