"At home [in Europe]...moral relativism, bred by years of pampered prosperity, was creating its own destructive forces. Again, egged on by intellectual elites, Europeans were encouraged to despise the civilisation that had nurtured them."
Great piece! And obviously sadly true of many of our fellow Americans as well.
The best thing to do is to hand it right back to them. After all, they have their own moral code, don't they?
Just tell them that their code is subjective and you don't have to bother with it. You have your own code.
The same idea works against them when cultural issues come up. Just tell them they don't understand your culture and that criticism of it is wrong, intolerant, and hateful. Use all the lefty-code they use against them.
Tell them, "my culture recognizes marriage between and man and a woman only and your forcing your culture on me! Don't be a cultural imperialist!"