Some years ago it was illegal to broadcast Gerry Adams speeches on the TV or radio, as he spouted his version of the truth of life in Northern Ireland. So voice over artists were used instead to speak his words. This generated an uplift in the number of people who heard his message as they were now interested in the way the broadcasters were getting around the ban.
This is an example of how it often makes more sense to let people protest, even if their messages are totally objectionable, than it does to make their message board illegal.
With the ban of Islam4UK, an organisation that openly peddles nonsense, hate and radical versions of their beliefs, we are possible scoring an own goal as far as the security services are concerned. Currently the authorities know who is involved and what their medium and message is. Forcing them to move will only make it more difficult for the security services to maintain effective efforts against them.
Instead: deny them the oxygen of publicity, and don’t create opportunity for their tale to be told.