[everybodyknows]

The meaning is that scoundrels, when confronted with evidence of their unanswerable crimes, will instead answer a different question: "Do you support some unquestionably virtuous cause?"

This is the reason that that runners of big cons typically give very generously to charities. See Anthony Trollope's "The Way We Live Now".

[eklavya]

Oh, I understood it differently. So it means that some scoundrels will use some virtue (in this case patriotism) to hide behind and not that patriotism is a bad thing?

[Koshkin]

I wonder if this particular 'virtue' has ever led to anything good. There is a parallel in the difference between, say, love (for one's land) and faith on the one hand and patriotism and (organized) religion on the other - the latter ones have invariably been used directly to promote hatred and intolerance in support of some political goals or in justifying criminal acts.

[eklavya]

You seem to be defining the "nationalism" being discussed here.