RogerINtheUSA commenting on a pro-charge article in The Guardian:

The congestion charge is of course a problem for lower-income people who are therefore dissuaded from driving their miserable little cars into London, but by keeping the riff-raff out you reduce congestion and allow the better people to drive their Bentleys and Jags to their important destinations without having to endure traffic jams.

[Resistance is 4x4 futile]

There are plenty of ways of reducing car use without disproportionately penalising those on lower incomes, such as closing roads to all but essential and service vehicles; priority cycle lanes (and I mean lanes, not just a narrow section of the road); reintroducing buses that people actually want to use; banning over-sized cars such as 4x4s; and running US-style school buses.

Of course, all these would cost money, while the congestion tax is a nice little earner. I'll get my coat.