Why would it be too late after an attack to HF? A few txs get stolen or blocked?
For a similar reason you're giving not to pre-empt it: building support for the new idea. It's possible that too many people will be psychologically impacted by the success of the attack, and consequently do what you're suggesting is wrong with my approach (despite the fact I've made no emotional arguements at all): allow emotions to dictate their decision instead of reason.
If we engage people to support pre-emptive action, a determined mindset would replace a fatalistic reaction. It's about harnessing a positive psychological feedback loop instead of a negative psychological feedback loop.
By my estimates 95% won't preemptively fork the PoW algo ... do you really think you can convince them all to preemptively HF?
Including Bitmain's current hashrate %? Clearly not. A PoW fork only needs to get the support of the miners who don't want to be ruled by a malign majority, although I'm seeing an obvious problem; how to measure that. Setting a block height activation would invite counter measures. Not sure how it could be achieved.
It seems like you're calling for a marketing campaign. You may be right that this is what needs to be done, but I don't think a bunch of technocrats will be able to successfully carry it out.