Earlier quoted context omitted.
You didn't cite examples either, and I'm skeptical of the premise. If reddit started redirecting /r/the_donald links to anti-Trump propaganda, or Youtube started redirecting his own videos to anti-Trump propaganda, no matter how good that propaganda is, I don't believe you that you could change their mind. And those people aren't even radicalised.
I don't have any sources either, but I'm sure that there will be different reactions to such redirects, depending on the individual. The hardened core will probably feel justified in their beliefs by the attempt to combat them and radicalize even quicker. But more casual group members might actually change their mind if they are confronted with outside opinions, especially if they hadn't considered them before. So wh…
Not if they are literally being tricked into being lectured, that's not how you convince any sane person of your credibility, it's, in fact, a giant disservice to your credibility.
You don't convince people through forced lectures, you convince people by engaging with them on an even level discourse to reach a common understanding of the issue at hand.
Also consider the reverse possibility of your scenario: What happens when somebody from the "good side" wants to see what opinions on the "bad side" actually look like? Such a thing might become impossible because every search will only lead to the supposedly "good opinions".