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?
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.