There is NO harm in using detergent oils in a two-stroke. The harm comes from using multi-weight
oil (like 10-30, 15-30, etc.).
Here's the factory's own publication regarding oil requirements in the their engines:http://www.detroitdiesel.com/support/on-highway/manuals/Lubricants_Fuels_Coolants/7se270.pdf
Also, if you do a search under "oil" and using Russ as the author, you'll find a post I shared a little while ago with an explanation about multi-weight oil.
Do the research, lots of "old wives tales" out there.
Personally, I prefer not to second-guess the factory on this one.
FWIW & HTH. . .