Yeah my understanding of genetics is pretty crap :) I decided to not bother poking at the assumptions they were making about the possibility of simple easy small "improvements" to genetics since that's not something I can poke at with much authority, and even if you accept that premise their argument is flawed.

I'm completely confused why having one's genes tweaked would affect free will in any way.

It does seem pretty bizarre an idea. They may have invented this as a straw man argument. Then again people have made some pretty stupid claims about clones.