If You Deliberately Wanted to Destroy the West and Its People

1. You would promote migration by nonwhites, but not too much, too fast because that would cause a quick collapse, then expulsion of the nonwhites. You'd want the apocryphal frogs in pots to feel pleasantly warm, as if they were falling asleep in a whirlpool bath. You'd emphasize migration by poor character, fast breeding nonwhites. But you'd mix in some higher character nonwhites to use as poster children and to help prevent a quick collapse.
2. You would try to make biocultural Marxism off limits to criticism, especially its policy prescriptions. 
3. You'd have some multiculturalists act as tough minded assimilationists, though there are few policy and consequentialist differences between assimilationists and other multiculturalists.
4. You'd get whites to hate one another and to hate their ancestors for specious reasons.
5. You'd redefine patriotism as support for globalism, cultural Marxism, reckless militarism, and following orders.
6. You'd take over every major Western institution from within.
7. You'd try to make dysgenics off limits to criticism and eugenics off limits to fact facing.
8. You'd welcome Muslim migration to China, Russia, and the West, so those nukes eventually end up with Muslim fingers on the switches. In the meantime, you'd encourage misanthropism, so egoism and reckless militarism controls the nukes. You'd call criticism of bioweapon engineering a violation of scientific freedom.
9. You'd distract the population with hedonism and techno-utopianism.
10. You'd create policy and environmental circumstances that are pro-natal for nonwhites and anti-natal for whites.
11. You'd praise interracial couples as an ideal, but only when the male half of the couple is nonwhite or Muslim or both.
12. You'd promote massive economic redistribution to globalized pseudo-citizens at the top.
13. You'd use policy and culture to encourage polygamy, endogamy, philandering, and single parenting. You'd make philandering look like sophisticated aestheticism.
14. You'd encourage useful followers to fight on behalf of the things destroying them.

In short, you'd do pretty much what the establishments are doing right now.