Ironically, the British action to ban him, has probably highlighted Wilders' position far better than it could otherwise have been.
The supposed reason for Wilders' being denied entry was "public safety," which was ultimately a response to outrage from the vocal Imams in Britain.
Sometimes, there's no better way to demonstrate the stupidity of somebody's demands, than to follow them exactly.
And ... knowing that the British have historically been very, very cagey in such matters in the past, perhaps that was precisely their intent.
You make a good point, banning him because he might cause civil unrest makes a very good case that Wilders is correct about radical Islam being violent. The trouble with your interpretation is that in terms of cageyness has somewhat dissipated in light of their subsidies of and acquiescence to radical Islam in their culture. So, I really think they’re just being pigheaded about arresting him.
On the other hand, the BNP is featuring the story on their website.