I do not believe this (or any) "broken-family" explanation for behavior is aimed indiscriminately at the mom. I believe that single parenting is the cause for many of the problems in our society, but I do not blame moms exclusively for the problem. Blame for single motherhood can lie (on a case by case basis) with mom, dad, both, in-laws, society*, etc.
* Society at one point in time frowned on divorce and this pressure prevented many couples from getting divorced. Society is more accepting now and enables more divorces (as well as out of marriage "families".)
I think you are more gracious than some on this thread. I'm not sure that all are so generous in their thoughts.