Switching gears in an automatic car while moving?

Now I know that people have asked this question before, but switching from drive TO a low gear to slow down. I want to know if it is bad to switch from low to drive without stopping. Normally I stop at a stop sign and stop completely and switch, but I want to know if it is bad if i dont stop and switch from L (at the bottom of the list) to D (near the middle)
My car is an automatic transmission.