In the case of Libya, the notion that we should not act to confront injustice and do good in situation A because we haven't acted in a similar manner for Situation B, C, and et al. is simply a fallacy on both a rational as well as moral level.
The messages sent from the Obama political operation suggesting the health care reform bill's historic significance largely served to underscore that a year after passage, it is not really historic at all.
Maybe at some point Obama will make some sort of address to the nation, and maybe he won't. Chances are, if he does, our involvement in Libya will probably be couched in the same euphemistic terms we've already heard.