Some of you will have seen this entry from notes on rhetoric:

Turkey - If your opponent is criticising the policies of some state you favour, demand that he talks about Turkey instead. This may sound a feeble ploy, equivalent to saying ‘please talk about something else’ but can be effective if you use language like ‘if you’re being consistent’ ‘disproportionate and selective attention’. (You may if you wish substitute some other country for Turkey – obviously so if, by chance, your opponent is talking about Turkey

I received a brief email recently asserting that it’s perfectly reasonable to ask that someone who is talking about abuses in country a address themselves to far more sever abuses in country b.
Well, except that your criterion for talking about regime a is not simply the severity of the abuses but, precisely, the likely consequences of speaking out about regime a, as well as the complicity of your own government (ie your representative) in the abuses of regime a.

Those who favour the Turkey ruse might consider applying it to other areas of their lives:

“How dare you criticise me as a parent when there are far worse parents overseas about whom you are scandalously silent!”

That's not to say, of course, that people can't be quizzed about why (strategically, pragmatically, ethically) they are criticising this particular regime. Indeed, the question 'a rather than b?' might be supplemented with 'now rather than then?' Why are you suddenly criticising Chavez now? Come, Is it your own devising? How is it that the free movement of your own intellect happens to coincide exactly with the interests of the US administration? etc.