Why do liberals keep going to war ?

An article at AlterNet discusses the "slippery slope of humane intervention" -

Liberal hawks never seem to learn that you can't get healthcare, decent schools and less unemployment by bombing smaller nations. Military adventures trump domestic rehab every time. We Americans have a very long history – going back to Teddy Roosevelt in Cuba and Woodrow Wilson in the first world war – of progressives going to war for the best, most irreproachable, humane, idealistic reasons, whether that meant saving Belgian babies from fiendish Hun bayonets or rescuing Benghazi civilians today.

It's extraordinary to watch progressives like NBC's Rachel Maddow, the New Republic's John Judis, Kevin Drum of Mother Jones, Juan Cole and many others cheerlead the "Obama doctrine" of humane intervention – that is, meddling militarily at "low cost", usually ending in disaster for all concerned. Such liberal war hawks have serious records of fighting for good domestic causes. But what a disconnect!...

We are no longer an infinitely rich country. Our bridges, dams, pipelines and roads are falling apart. Our people are on food stamps and can't find work. Spilling our money on the desert renders it positively reasonable to cut, slash and degrade – that useful military euphemism – help for the poor and middle class...

The arithmetic is brutal. Each Tomahawk cruise missile fired from a sub, ship or land costs roughly $1m, and we've probably shot over 200 of them onto Libya... The Centre for Strategic and Budgetary Assessments estimates that the Libyan operation costs the US between $100m and $300m per week, so we're heading toward the $1bn mark even if, as advertised, we pull back marginally....