I don't understand the argument that there is a danger that hypersonic weapons will be developed to carry nukes. That weapon already exists, it's called an ICBM. You might have heard of them. ICBM reentry vehicles are already hypersonic [http://en.wikipedia.org/wiki/Intercontinental_ballistic_missile] . Some reach peak speeds of mach 20. That's one of the reasons why they're so hard to intercept.
Also, BTW, the Russian's already have hypersonic anti-ship missiles (http://en.wikipedia.org/wiki/P-800_Oniks, mach 4.5) so apparently the goal of this treaty would be to stop us from developing weapons that already exist? Or just maybe to prevent the U.S. from developing weapons to match Putin's stuff? Sounds like a worthy goal to me. Maybe we should step this up to block the development of all "chemically powered weapons" (ie, guns and missiles) because they sound dangerous as well.
PS: The fact that hypersonic missiles are hard to intercept doesn't make them any more of a "1st strike weapon" than what we already have.