I'm not as against them as no mercy. Because not everybody needs to "do it right"
There are lots of people out there who are hunters, not shooters. And lots of people fill their freezer every year doing things that aren't correct when it comes to shooting. And that's their goal: fill the freezer.
There is historically plenty of reports of broken stocks and scopes that are attributed to sleds. And that's something to consider. Also, it's really not hard to develop good shooting form and to shoot acceptably well with a couple of bags.
But they sell allot, and allot of people use them.
-Jake