"Validity" is a matter of perspective and depends entirely on the choice of code you freely choose to run.  Those small number of people currently transacting with BCH aren't doing so to intentionally trade invalid tokens, for example.  They're doing it because they want to and feel sufficient incentive to do so.  As such, I don't think anyone is suggesting that the most-work chain can force a change of consensus that a supermajority of users opposed.  It's more a question of whether the supermajority of users:  

a) really is a supermajority, but we can't put the cart before the horse and assume that it is

and

b) whether or not these users' preferred chain would have sufficient transaction volume to be a greater incentive to the miners than the forked chain the miners are proposing.

My argument is essentially that users and miners are free to leave if they feel they have an economic case to do so, but those who want to remain on the original chain don't have to change a thing (with the possible exception they find themselves short of hashpower).  It's then down to the users and miners of the original chain to prove them wrong, because that's how a market works.  You can't just claim you have the superior software and try to prevent them from leaving.  You have to allow them to leave and then realise their mistake (assuming it does turn out to be a mistake).  After all, it's their hashpower they'll be wasting if their new chain doesn't have enough traffic to sustain it and make it financially viable.  One way or another, there will be a natural and organic alignment of incentives.  There could be a winning and losing chain, or both chains could survive resulting in a permanent split.  Either way, though, it'll be resolved and every participant can weigh up the pros and cons and decide for themselves what they want to do.

Admittedly, there is some risk for inexperienced SPV users if they aren't paying attention and a risk for any inexperienced users, full node or not, if they tried to move their 2x coins without taking adequate precautions.  But anyone who has access to their keys can ultimately choose which chain they want to follow.  

We should certainly recommend not transacting whilst all this upheaval is going on unless you know what you're doing.  

But still, the far larger risk is to all those countless users with their funds in the custody of a "trusted" third party like exchanges and webwallets.  They're the ones who need the loudest wake up call, since they're the ones truly using Bitcoin in a way that wasn't intended by design.  They are entirely at the whim of their custodians as to which chain(s) they may or may not have access to.