1. I don't really give a shit either way when I encounter one but as a businessman I am against them as something I should have to pay for. My points were twofold:
A> there's a games theory/cartel issue around "best practices", and you basically have no liability if you provide the "standard of care". This is true in security practices, medicine, etc.
And B> there is often an incentive mismatch between the implementor of a process and those subject to it which biases aggressively down or up, against gradualism. The most visible extreme is TSA in which the risk of letting a shoe bomber is extremely high (i.e. the decision maker would lose their job if it actually happened) while the cost is borne by all the miserable travelers who, realistically, fare essentially epsilon risk of actually encountering such a device.
With regards to your point B, I'm happy to remove my shoes if it reduces my chances of being killed in a terror attack from (making up numbers) 1/1M to 1/1.05M. It's just that it's unclear whether the TSA's screening methods are effective, and/or optimally-effective, and/or optimally-effective while minimizing passenger inconvenience. (They're probably at least somewhat effective, at least as a psychological deterrent, seeing as there hasn't been a successful terror attack on a US airplane since 9/11).
Correlation does not equal causation. There also have been no successful terror attacks on a US airplane since they 1) Implemented reinforced cockpit doors, 2) stopped allowing people to line up for the forward bathroom, 3) added air marshals to the planes, 4) implemented TSA pre-check.
So we have no idea, if any of these, has actually improved security. It's possible that just no one has tried since 9/11 because there was no reason to.
And "probably" doesn't equal "certainly." It's certainly within the realm of possibility the TSA's screening methods are ineffective.[1] But given the 16-year perfect record[2] in preventing not only hijackings but also bombings (which cockpit doors, air marshals and bathroom line policies are powerless to prevent), it's only reasonable to say their methods probably have some effectiveness to them, which (repeating myself here) is not to say they're the best possible screening methods. And there are most certainly people who think there's "reason to" attack US airplanes, hence the foiled incidents (shoe bomber, liquid bomb plot, underwear bomber) that engendered the more annoying TSA screening policies.
[1] Although I'd say the more likely problem is that the personnel doing the screenings may be ineffective, rather than the fairly-standard-worldwide screening methods they use.
[2] Which in all honesty is quite impressive. Immediately after 9/11 I'd never have guessed we'd go 16 years not only without another 9/11-scale attack, but no attacks on airplanes at all. It's not yet as good as Israeli airport security's 41-year perfect record, but it's nothing to sneeze at.
2. LCD = lowest common denominator in this case?