I have a big problem with this. Cycle lanes are not in any way part of the road infrastructure, they are ghettos where those of a car-centric society want to place those they are excluding from the road user's society.
Yes and no... I take your point about ghettoisation of cyclists, but if you look at somewhere like Blackfriars Bridge, the introduction of cycle lanes (segregated by a foot-high kerb) has reduced the amount of roadspace available to other traffic, which hopefully discourages motorists from using that route. (Of course, the Blackfriars cycle lanes were a side effect of traffic reduction measures for other reasons rather than the result of pro-cycling policy, but the net result is the same and shows what could be done if the will were there.)
Even as a fearless Lycra-clad Urban Road Warrior who doesn't bat an eyelid at negotiating Elephant & Castle by bike, I would favour routes free of motor transport if I had the option.
However, I've taken note of Red Light's interesting point about the reduction of cycling in Dublin. The argument in favour of segregated lanes tends to be that more people would cycle if they had that protection. Maybe it's more complex than that...
They are an all too easy sticking plaster to remove the victims rather than deal with the issues of sharing the road.......and unfortunately exacerbates the already poor situation by reinforcing the concept that cyclists don't "belong on the roads"
...and this is why. Building proper infrastructure shouldn't be a standalone measure - it should be carried out in tandem with a campaign of education to improve the behaviour of motorists towards more vulnerable road users (pedestrians as well as cyclists), as well as further restrictions on motorists to make driving an even less attractive option in cities (and much stricter enforcement of traffic infringements by motorists).
So despite your valid concerns, I would be strongly in favour of more cycling infrastructure in London - as long as it were implemented in a way that genuinely promoted cycling and discouraged driving.
d.