And are instead simply adopting the right's use of the term as a catch-all slur.
"The left" is not supporting Assad. The left is pissed that we are getting involved, and more that we are backing a faction certain to cause as much damage as Assad ever has. Similarly in Mali, the problem is the civilian deaths being incurred.
Maybe you should look at the people who believe all war is justified and that "collateral damage" is just something you note on a spreadsheet, if you want to find the actual problem?