I've been unable to pin down the exact form of words he used, but this morning David Cameron told Jeremy Corbyn an elementary moral truth (see entry at 11:28):
Jeremy Corbyn, Lab, wonders why we are getting involved in Libya, when there are so many places worldwide that suffer human rights abuses. David Cameron argues that "just because we can't do the right thing everywhere, doesn't mean we shouldn't do the right thing somewhere"...
Or was that 'anywhere'? Whichever, it's an obvious point. The fact that Corbyn's question is so common is the result of a tendency to conflate the reasonable demand for a proper degree of consistency and impartiality in the application of moral principles with the not at all reasonable demand for people to display an impossible amount of energy, time, command over resources and so on, by generalizing their actions for the good so as to benefit all parties who might be thought appropriate objects of them. This tendency is wrong-headed, requiring as it does superhuman levels of capability from those of whom the generalizing actions are demanded. It's as common as it is, not because of any real belief in such impossible levels of capability, but because it's a quick method of trying to embarrass people you disagree with. But it's also a useless one.
It occurs to me that the argument I'm making here might be invoked on behalf of people calling for a boycott of Israeli academics and only Israeli academics. But this appeal would be in vain. Apart from the fact that boycotting academics because of the policies of their governments is not an action for the good but an unjustified punishment of individuals irrespective of what they think or do, academic boycotts, were they justified, could be generalized from one country's academics who putatively deserve it, to a second, and a third, and a fourth etc, without this putting a strain on the resources of the boycotters - in the way that taking military action does involve such a strain. No country, or even coalition of countries, can realistically contemplate military interventions against a large number of seriously rights-violating regimes all at once. But would-be boycotters could decide to have nothing to do with the academics of any number of countries they think deserve this, by just not doing anything to liaise or cooperate with them. Those who single out Israeli academics for blacklisting have still to explain why no other country is worthy of their attentions, when it would be so easy for them to generalize these.