Khan did say that very thing and as much as I dislike him he did torpedo the argument with that line.
That said, the ulez in central london has support because the very wealthy can drive and pay the charge or easily afford to upgrade in the unlikely event they are not compliant already. Everyone else can get about relatively efficiently without needing to drive so apart from a small band struggling with older cars why would you not support it?
Start pushing the ulez out into the suburbs and it’s a very different matter - you are really hurting the less wealthy with no alternative transport means, you’re hurting the middle ground who can afford to, but resent being forced to pay considerable sums to upgrade, and of course the very wealthy are unaffected for the same reasons as the wealthy in the centre.
We’ve got the ulez coming to 3/4 of a mile from my front door. Every single person I know has a compliant vehicle already and will be unaffected so should have no reason not to support cleaner air, but the paradox is the expansion plan is absolutely hated.
There will be all kinds of theories around that, but my view is despite the blue rinse stereotypes there is genuine anger that those struggling to keep their older vehicles on the road to get to work, or get their kids to football training after school, or.. (etc etc) will be forced off the road with limited alternatives and motoring will become the preserve of the wealthy.
If that view is seen as just an unfortunate byproduct and a price worth paying then press on, but don’t be surprised when you get a kickback like Uxbridge.
It’s a bit of a warning to everyone forcing green issues despite good intentions. You have to pick you battles wisely and I think Khan has got it wrong on this one.