Because maybe the word "their" will be replaced with "other peoples"?
You might think "such a person won't care about patents", but I can think of many nightmare scenarios, which a common criminal will be able to do if such a thing were possible.
It's bad enough with the drugs that already exist.
Well, that's how technology works. It's a rare device or procedure which can't be used as part of some nefarious plan, but that's no reason to ban or suppress the devices or procedures.
Obviously I can't be sure, but I think the level of success had by nonproliferation of nuclear technologies is indicative of what we could expect from that, and I don't see any strong evidence of it.
If this is reliably applied to humans, well, the implications are just staggering.