There is no law against using someone else's USB VID, as long as you don't put a USB certification logo on your product.
What FTDI did, on the other hand, is malware and clearly illegal. It is destroying private property and I guarantee violated multiple laws in many countries.
I don't know the laws elsewhere, but here in Europe trademark holders absolutely have the right to demand counterfeit products be seized and destroyed. Even if the owner acquired them in good faith. Also it would be interesting whether any compatible chips exist that use FTDI USB VID but were not marked with the FTDI logo.
Of course this kind of vigilante justice by FDTI is illegal, but who is going to press charges if that means they will get their devices taken from them and destroyed?
Right, we're talking about clones that don't use FTDI's logo. I don't know if they exist, but they well might. The point is that the VID itself doesn't have any legal protection.
What FTDI did, on the other hand, is malware and clearly illegal. It is destroying private property and I guarantee violated multiple laws in many countries.