Earlier quoted context omitted.
But that's just turtles all the way down. The Fed can mine that forked chain even more easily than the original one. When one actor has a money printer they can use the permissionless, decentralized nature of the bitcoin network as a weapon. It's a vulnerability they can exploit.
Regardless of how much money can be printed, no government has enough resources to attack a perpetually moving and atomizing target. As long as governments debase the currency to carry out this attack, they are also continuously creating more reasons for variations of Bitcoin to exist.
This is something the Fed does all the time, this is exactly how they distort the economy to set interest rates and bond yields. They have been 51% attacking the bond markets for decades, and all the bond shorts who thought "they can't possibly keep printing at this rate" lost their shirts.