I really like this question, I couldn’t possibly get to the bottom of it but here’s a couple of half-explanations/related phenomena:

• The simple desire to own the libs. They understand what freedom and personal responsibility is, but also really, really want to DEBATE ME BRO with someone that they don’t like.
• Legitimate paranoia that one day somebody is gonna 1984 them, so they’re morally responsible for constantly pushing social boundaries.
• Virtue signaling, like the post alludes to.