Because if I stop at the lights, shift into neutral, the auto stop won't work. I would have to manually restart the engine.
Yes it will. As I have already pointed out
selecting neutral does not restart the engine. Nor does it interfere with idle stop in any other way. The engine will restart perfectly well if you release the footbrake, move the gear selector to any other position or adjust the steering wheel.
I did actually email Honda about this shortly after I got the car however their response was pathetic. They just reiterated what the manual said about idle stop, completely failing to address my concerns.
But..as I noted - not applying the handbrake is endemic these days. Almost no-one bothers to take their foot off the foot brake when stationary. It's possible that the vast majority of drivers are now driving automatics but I doubt it. It's valid to complain about the design of idle stop but choosing not to avail yourself of it or suffering the hassle of manually switching off seems silly. One less set of brake lights in a traffic queue is not going to make any difference.
As for the law it makes sense to me. As another poster said: The rule is that you mustn't dazzle other users with your brake lights but if properly fitted brake lights are designed not to dazzle there is no problem. I can honestly say that brake lights in my eyes have never been anything other than a minor irritation. Anyone being genuinely dazzled is either behind a car with defective lights or needs to see an optician.