Whether true or not, Dell's policy is wise.
It is bad form to trash your competition to your potential clients. You may gain a little in the short-term, but at the sacrifice of your own long-term image.
Possibly true in general terms, but on an issue this controversial I'd say it depends greatly on the predisposition of the audience. Dell probably did the right thing by offering an apology, but in some regards that apology also gives this issue further wings.