Getting wildily off-topic, but I believe it's specifically James Ferman, long-time head of the BBFC, who had a problem with the word 'ninja' (automatica 18 rating for including that word in the title!). He also hated chainsaws, nunchuks and, I think, flick knives.
To his credit, there is soemthing about the appeal of certain weapons. I have a very vivid memory of seeing Face/Off while on holiday in Greece in 199whatever year it came out, and there's a scene that was definintely NOT in the UK version where evil John T shows his daughter a butterfly knife opening up - and it was just about the coolest thing I'd ever seen. I immediately wanted to buy one and stab all my friends.
(All of which is less funny than an epsiode of Low Life, but more interesting than an episode of Nemesis and Snoozelock)