The whole debate is held as though cyclists were some other group. This is rubbish, and on the garbage in, garbage out principle, if you don't understand the problem first you aren't likely to produce an effective solution.
Cyclists are motorists on bikes. Common sense confirms this. Of course someone reading this is bound to reply that they don't have a driving licence, but if we asked all participants here to declare the answer to that question, we all know what would happen*.
So a more useful question is, do motorists behave differently when they climb onto bikes, and if so, why? And if they do, does that betray a false belief that a bike is not a proper vehicle? And if so, does that affect how, when they are driving, motorists in turn treat bikes?
I'm reluctant to comment in detail on the very sad case above, as I only know what has appeared in newspapers, and that's probably not very accurate. However, 17mph is clearly not fast in general, since 18mph is the speed at which cyclists should move off cycle paths onto roads. Others have made the very good point that having a reasonable expectation that others should move out of the way does not of itself mean that you should not yourself do everything possible to prevent an accident - and it's not clear that the cyclist did. And maybe this supports the idea that bad cycling should earn penalty points on a driving licence? (Because it's 99:1 that the cyclist involved is also a motorist.)
*I'll start. I'm drossall, and I've got a driving licence.