Be hyper alert about what they watch. Don't let anyone, including grandparents or other influencers give you any shit about it at all. Be very firm and very aggressive about it. Be an asshole about it. "Timmy can not come over to your house again if I find out he watched anything not approved" My inlaws are awesome people, and while they're conservative, they're completely asleep to what's going on. They didn't see the big deal in letting my kids watch whatever kiddy nonsense was on Netflix. And being boomers, their world revolves around the TV. The kids came to associate them with TV so heavily that even when they visited us, our otherwise well behaved kiddos would throw tantrums expecting TV. It got.bad enough that I had to threaten to cut them off from seeing the kids at all until they were older if they couldn't respect our wishes about screen time. You and your spouse are the boss and you must make everyone respect your parental strategy. Fortunately things are better now and the grands are actually getting to know the kids instead of just spacing out together.

Anyway, also put them in well vetted private schools or homeschool them.

Most importantly, instill in them a faith in God and a working world philosophy by which they can identify and reject the world's bullshit when they get too old to be fully protected anymore.