Not saying there are never cccassions where curbing it or limiting it can't be okay, the classic case of yelling fire in a crowded theater, but when in doubt, let 'em talk. The ethics is the only relevant matter anyway, liberty isn't supposed to be selectively applied, but from a practical standpoint, sticking fringe types into the sunlight tends to make them laughed at, and people on the cusp will avoid them because of the ridicule. Keeping them gagged makes them matyrs, and people on the cusp will race to join them.

That's my take as an american, I really don't know this organization nor the guidelines the BBC works under, nor your particular laws on freedom of speech/assembly/press/etc, except that they have presumably changed quite a lot since 1776.