Most of the rationale based around that is market-centered, related to the potential of somebody "dumping" these coins and this is not a very convincing line of argument for anyone who is maximalist-oriented.
You're stating an assumption that many people seem to be holding. It's a naive assumption. Note that the BIP says nothing about market dumps / sales / etc. If a market dump by a quantum attacker was the only worry then you'd be correct, it would just create some temporary pain and we'd move on. I'll be addressing attack scenarios in my upcoming series of essays.
My focus on that statement is solely on historical coins like satoshi's. Scenario (for the question/statement):
Assume that users and entities have upgraded (better) or been pushed to upgraded (worse), then there is no rationale for freezing those coins other than market related talk. What other harm could those coins possibly cause to the network or protocol? They literally can't do anything. For all we know it could be satoshi reintroducing his coin, which are assumed to be lost/dead, back into the circulating supply. This has no effect on the network from a technical standpoint.
In regards to the other coins and the situation where users and service providers are getting randomly and suddenly hacked and the ensuing chaos -- there I do agree there are existential level worries. Although even there, as I have noted previously elsewhere, users would be able to submit transactions privately to miners until things resolve. We would take a massive hit (and this kind of chaos is best avoided if possible), sure, but it is not like suddenly you will not be able to transact at all unless you want your coins to be stolen.
"Lost coins only make everyone else's coins worth slightly more. Think of it as a donation to everyone." - Satoshi Nakamoto
If true, the corollary is:
"Quantum recovered coins only make everyone else's coins worth less. Think of it as a theft from everyone."
You literally quote this in the BIP, and this is a market implication. While you may not be using the exact wording, this is the implication but anyway as I said my statement was focused on those coins.
You need to convince them too if you want to have any chance at all of reaching consensus on something like this. If you can't convince them, this is not going anywhere. The best alternative is to fork Bitcoin with such a proposal, but that historically has not worked out well for those that did do it.
Given that this is a soft fork, rough consensus will generally come down to hashrate and major economic players.
Which seems like a good thing to you? And for me it is quite a terrible thing.
If we can demonstrate that freezing can be done with only hashrate and the major economic players (the fewer the easier),
then we will have made a case for government-forced freezing. Forcing users into compliance-consensus to do something like this with a hard fork is near impossible practically speaking, but successfully doing it with a soft fork will create a precedent that we will never be able to fully get away from. We can only hope that collectively we will be able to defend against a future freezing mandate, but
shifting from decentralization guarantees of censorship-resistance into hope is not exactly an improvement. Is it?
I'd prefer some dumps in the million range over turning into something like Bittether any day.
As of today, the threat is distant and thus no one is interested in activating such a proposal.
My thesis is that individual economic incentives will trump philosophy in the face of existential threat.
In terms of entities or users upgrading fast to new address formats? Sure, I hope so to. In terms of freezing balances? I hope not.
