I cringed when I read that. A splash of water is ok, but scotch is only drank on the rocks if it's mixed. If you really want to have it cold put a glass in the fridge serve your ambient temp scotch in it and let it stand for a minute or two.
I also don't think it is such a cut-and-dry issue as some people make it out to be. Macallan even produces this: http://www.notcot.com/archives/2010/01/the-macallan-ic.php
But the guy above was talking about drinking single malt scotch on the rocks. It's not the temperature.
Single malt is enjoyed because of its taste and character, but if it gets mixed with enough water, from melting ice for example, it breaks and loses its appealing qualities.
Single Malt + Water = Former Delicious Whiskey. But in an emergency, you can use ice to make some awful blended whiskey potable.
Edit: OK, maybe you confused me twice, first by seemingly cringing at me, and then by talking about "mixed" whiskey. I guess you may have meant that the post I was replying to made you cringe.