Cycle campaigning

Does anybody know whether any cyclist accidents would have been avoided if the victim had heard and absorbed this advice beforehand?

There's no doubt that some deaths might have been avoided if some people had had this advice before and heeded it. A large number of deaths wouldn't have been avoided, though, e.g. when a lorry overtook a rider from behind around a corner. (I know you're not blaming the victims--neither am I.)

If that message can be spread more and saves one limb or life then it is worth it in my book. Campaigners can still fight for the other aspects. Can somebody please explain to me why this is not worthwhile to persue this message more aggressively?

It's always worthwhile to spread it, and it's pretty much the first thing we tell people:

http://www.no-more-lethal-lorries.org.uk/

Danger zone:

Ive had this debate with an LCC member and he said it was a bad idea because it might put people off cycling...is that really such a big deal if it saves lives in the short term and reduces cyclist number if we succeed in making London a safer place in the long term so that more may feel safe to cycle then?

It does put people off cycling to be told that cycling is dangerous, which it isn't, but it is certainly not a problem to tell them about this very specific danger. The person to whom you spoke either didn't know what they were talking about, or you misunderstood something.