The only sensible basis for a case against intervention is that it is ineffective or counter-productive. Well, sometimes it is, but to say we have a duty to intervene does not mean we should always do so, without any regard for the consequences.
The odd thing about this debate is that there are two groups for whom anti-intervention is a rational, consistent stance to take. One is market fundamentalists, who believe that the only way to improve the world is through the invisible hand working through free trade. The other is narrow nationalists who believe that we only have duties to "our own". That these people should be lining up with critics of interventionism on the left is a sign that something is wrong.
The problem with this is that it’s a straw man, the only people who oppose intervention outright are “market fundamentalists” and “narrow nationalists”.
In the past I’ve found myself arguing online with left-wingers opposed to intervention in places like Iraq and the Sudan, but in every case their opposition sprang not from a rejection of the idea of intervention but from the belief that intervening would only make the matter worse – they felt that the selfish motives of the UK and US would see civilians sidelined in the pursuit of oil/influence/etc. I’ve never encountered anyone who didn’t feel that we had a “duty” to help those in need.
The actual danger is in the widespread knee-jerk cynicism that holds that the west is incapable of acting in a humanitarian fashion.