Temperature can be controlled using steering wheel controls. You do need to use the touchscreen to activate the defroster, though. I don't personally find it to be a problem, as the controls are right at the bottom (removing a dimension) and I never used the defroster often enough in other cars to be able to activate it without looking either.
That is just plain dangerous. There have been times that I needed the defroster, couldn't safely stop, and had to keep looking out of my rapidly-fogging window.
This probably doesn't happen where Tesla's engineering is located. The typical conditions are probably 100% humidity, then suddenly getting cold rain on the windshield.
