It doesn't seem right to count only the cost of implementing the low-traffic schemes (which is low) and not the cost of people having to spend more time and more effort in order to get to places. I'm not in London but I am in a city without accessible parking, so I walk to work every day. It takes me 25 minutes each way to walk about 1.2 miles. If I lived somewhere where driving to work was a realistic option, I could save about 40 minutes a day or I could have a lot more options when choosing where to live instead of living as close to work as I can afford. I used to be somewhere where I could drive four miles to work in less than ten minutes. There, if I spent the same amount of time commuting as I do now, the area where I could choose to live would be 75 times larger (since it scales with the square of the distance traveled). And, of course, walking is unpleasant most of the time, when the weather is rainy, too hot, or too cold.
So sure, living somewhere where I walk every day is good for my health. I would still much rather be able to drive.
I'll be frank. I don't seem to understand the justification for policies whose primary purpose appears to be a malicious desire to make life harder for those people still lucky enough to be able to drive. Smug, paternalistic articles about how preventing people from doing what they want to is actually for their own good don't help.
LTNs make life easier for everyone who doesn't use a car which, in inner city London, where many of these studies were conducted, means the majority. So, it's not about maliciously targeting people with cars but benevolently targeting the majority who don't have them.
I didn't personally find the tone of this article smug, but again: it's not about making life harder for people who want to drive or preventing them from doing what they want (because after all everyone can still drive if they choose to), but enabling people to safely do what they want when they want to walk and cycle. LTNs make walking more pleasant and safer; there's even some evidence they reduce crime! So, as you're someone who walks a lot but doesn't particularly enjoy it (sorry about that), LTNs ought to make things a bit better for you.
Finally, LTNs are about as likely to reduce journey times for motorists as they are to increase them, so the net effect on motorists way well be neutral. Again, this doesn't strike me as the kind of outcome I'd want if I were maliciously targeting motorists.
I agree that compromises between the interests of drivers and pedestrians are necessary, and in a big city with more pedestrians than drivers, it is reasonable for these compromises to favor pedestrians. I don't agree with the frequently expressed view that reducing the number of drivers and increasing the number of pedestrians is in itself a good thing, and that's what this article sounds like to me. The emphasis on the health benefits for people who stop driving feels like being told "eat your vegetables, they're good for you" which, as an adult, I'm offended by, but this is an emotionally charged issue for me so maybe I'm overreacting.
I'm interested in the claim that LTNs do not, on average, increase motorist travel times. That could change my mind about this issue.
I'm not entirely clear why you feel (re)designing cities around walking/cycling is a patronising policy, but designing cities around cars isn't. If the answer is, 'because cars aren't good for you', it seems like your stance would have to be 'cities should be designed around what's bad for you, otherwise it's patronising', and I don't think that can be what you believe!
I suppose it depends on what the "greater good" is. If I was doing significant harm or likely to do significant harm in a way that could only be prevented by not driving (for example, if I was a dangerous driver due to some disability) then I would feel a moral obligation not to drive. If, however, I was simply causing a very small part of a much bigger problem (such a pollution) then I would be open to paying a tax or fee to compensate for the harm I was doing, but I would still drive. I think I contribute to society and therefore I do feel entitled to use a fair share of society's resources. If I was merely offending the sensibilities of people who think that a society with fewer drivers is better in some unquantifiable moral or aesthetic way then I wouldn't feel any obligation to cooperate with them.