Actually, in California, you are. CA distracted driving laws don't distinguish between stopped cars and cars in motion. Reading a text (or, now, checking a map) while stopped at a red light is legally the same as doing so while driving down the highway.
It is the same way in Alabama. If you are stopped and are sending messages then that is just as illegal as if you weren't.
I think the idea is, if the light turns green, you might hurry to put down your phone and begin to accelerate. Meanwhile, someone may be in front of your car, and in your rush, you do not notice this and plow into them (pedestrian, traffic got jammed up in the intersection, whatever).