working against

EU and other anti-competition authorities MAY be persuaded to look askance at such a move.

The chance of this could be increased if Consumer Organisations and alternate O/S vendors (RHEL, OEL, etc) point out that this is anti-competetive lock-in, and that MS have significant market share, as the phrase goes, and that they used this market position to hugely increase the proportion of a PC's cost that goes on Windows over the past decade or two...

The MS move will harm Apple or any other potential MS competitor (and Linux is a competitor with economic importance in server space).

So, if regulatory capture can be avoided, that is one slow and unreliable route to oppose this MS abuse.

One solution could be to demand that purchasors of hardware (or o/s suppliers) be permitted to enable any other O/S they please, without charge, either on a case-by-case basis (with keys/signatures) or by turning off this "security". The former route would address the (transparently bogus) security rationale for the change - by preventing modified O/S from running WITHOUT permission.