A motherhood term is one that is accepted as good in any context. When attached to a specific policy or ideology by propaganda, it tends to reduce the probability of the policy or ideology being attacked, even if the person promoting it is not himself credible as a promoter of the concept referred in the motherhood term.
For example, many proponents of so-called "family values", including Ronald Reagan for instance, had been divorced, and thus arguably had experienced at least one serious failure of such values. Similarly, the Bush League which claims to be "tough on crime" has been closely involved in several large-scale criminal scandals such as the Savings and Loan debacle. The use of terms like "family values" when attached to specific policies on abortion, for instance, are potentially quite destructive to the real values of actual families, but this usually goes quite unexamined, especially as statistics are not usually available, and disputes even on such basic concepts as "family" itself may be at issue.
Given the ease with which motherhood-term based arguments can be turned back on their users, their use may have been declining in the 1990s after heavy overuse during the 1980s in North America. However, the War on terrorism brought a whole new range of motherhood terms such as Homeland Security and the old bromide "freedom" - which somehow justifies anything that compromises freedom in favour of the state's ability to investigate and detain anyone.