I think about this everyday, because it is very real for me and my son.
I challenge him. Anything he says that I discern as regurgitating the thoughts or dogma of peers, deluded adults, media, wierwillian stupidity... I ask him questions, I challenge him, I challenge the dogma, the opinions. I don't necessarily provide answers, because he gets enough "answers." The questions are what others are NOT "teaching" him.
Even if I agree with an idea he regurgitates, I ask him, "Says who? How did they come up with that? How do they know? How do YOU know? Why is the opposite false? Why? How?..." I try to challenge him to think about ideas, their source, what they mean.
He sees and hears so much of WHAT. What to believe, to think, to know. So I challenge him to think about WHY he should accept any of it. I don't always tell him outright WHAT to think, rather, I try to help him HOW to think. I try.
Occasionally, he will text me something he sees on social media. And he will simply ask, "BS?" This always warms my heart. He is 13. I always provide an answer.
I haven't yet taught him how to correctly spell beleeef, but one day I will.