Bull fucking shit. It turns fully-validating nodes into non-validating nodes.
A non-Segwit node can always validate transactions that are relevant to them. They do not validate the witness portion of Segwit transactions. They also do not generate Segwit addresses, nor do they participate in Segwit transactions. What you're talking about is moot.
The only real issue there is partitioning risk in the bootstrapping phase -- since Segwit nodes can't bootstrap from non-Segwit nodes. The solution for this (dropping non Segwit peers for Segwit peers in outgoing connections) has already been coded and merged.
Soft-fork segwit is (unless you were closely watching Dr. Backamoto's
extension block proposal) such an unexpected and refreshingly elegant optimal solution (IE pleasing to both 'sides') it doubtless grinds Gavinistas' gears that Evil BlockSchemeNorthCorea agent provocateur Lukejr was the primary author.
I predict the Gavinista Jihad against segwit will be just as successful as the one against OP_CLTV. That is, not at all.