I happen to prefer a thumb safety. Why all the fuss? If you don't like them, don't get one. I really don't understand all the Ink (or pixels in this case) wasted on this issue.
Yes, but you have to look at it in the context of what the safety does on other guns.
On a 1911, the safety blocks the hammer and sear. So, if the thumb safety were off, the gun will fire should the sear let go.
The thumb safety on the M&P only blocks trigger movement. If the safety is off, and the sear fails, the striker block will still prevent the gun from firing. So, when in a holster, the trigger is already blocked thus, if the thumb safety were knocked off, and the sear failed, the gun still won't fire.
You could call this an academic exercise, but the thumb safety on an M&P really doesn't add much to the package.