Good on FTDI for having a go and pushing the squatters off their driver, the device isn't bricked it is simply not recognised by their driver anymore.
For a layman, aka, consumers, and the vast majority of users of this IC are consumers, the result is indistinguishable.
Consumers just don't know, don't care, and need not to know or care what kind of USB chip is in their gadget. They buy the gadget, they don't have the knowledge to open it, diagnose if the IC is fake and they don't have the means and the skills to fix a bricked device.
FTDI was knowingly and willingly accepting huge collateral damage. They thought it was OK to kill heaps of innocent bystanders. It is now firing back.
Maybe a Scottish victim of FTDI finds some time to report FTDI to the proper authorities
Intentionally looking for a device which isn't licensed to use the software and disabling it from doing so sounds legitimate when you put it that way.
No, it isn't. It is vigilantism without proper authority. Turning off their own driver so it does not works with fakes, OK, fine. Manipulating the property of others, so laymen can no longer use that property, is not legitimate.
Further, even if the damage is not permanent, i.e. people manage to fix it, FTDI caused damage. Just because you can repair something doesn't mean damaging that property is legal.
And if you want to discuss legality further, the UK (and Scotland is still in the UK), has a chapter "
Unauthorised acts with intent to impair, or with recklessness as to impairing, operation of computer, etc." in its Computer Misuse Act.