You explantion is - Edit 1
Before modification by DomA at 20/03/2012 06:25:33 PM
I believe that the OP never "harm" SL at the Cleansing.
It most definitely did not, but my impression from the scene is that the conduit of saidar and saidin standing between the taint and SL is what prevented the dome of Taint from collapsing. It was like a glass plane between two rabid dogs. As soon as Rand and Nynaeve stopped, the two forces tried to occupy the same space/dimension, and they destroyed one another.
IRRC, Jordan spoke of the forces of SL/DO repelling and attracting each other at the same time. The collapse of the dome created a crater of no doubt the exact same volume as the Dome.
During the Cleansing, the two forces never came in direct contact (if they did, they would have destroyed each other right there. There was saidar between them. What Rand did was having saidin close enough to Mashadar/SL to cause the taint to separate from saidin.
Darius implies without the OP pressuring SL and the Taint together the two forces would not have come in contact, but that contradicts what Jordan explained.