GPS units like Garmin use touchscreen instead of physical buttons and are safe, road legal. Tesla ships cars with a huge touchscreen console - safe and road legal. That's a pretty weak excuse.
We could also debate that things that hinder concentration while handling "2 tones of steel" are :
I think display placement is much more important than size. Using a phone for nav that's sitting in your cupholder is terribly dangerous, but using one clipped to your dash inside your field of view seems okay.
Larger display and physical buttons are really quite a good idea when you're driving 2 tons of steel at 60mph.