Hmmm, mixed feelings on this tbh (leaving aside that the source is The Sun, so it’s probably all ■■■■■■■■ anyway).
Should cyclists be accountable? Absolutely yes, just the same as any other human whether they be piloting an aircraft, steering a supertanker, or driving a bin lorry, it matters not. As for number plates and insurance I’m not so sure; what about your five year old grand/daughter on her tricycle outside her house, should she have insurance etc?
I’ll also say that I think that we should actually encourage cycling (despite them being a right royal PITA) for the simple health benefits alone. I have no idea what one prevented heart attack is worth, but I’ll guess that it’s not a figure to be sniffed at.