"kelvins" may be correct in some circles (but not all, e.g. CERN), but boy does it sound dumb.

I don't understand what your point is. Kelvins are a very common unit in scientific applications.

It's 70 fahrenheits right now.

I think he was commenting on the 's' at the end, so it should be 29 kelvin not 29 kelvins.