“He can direct the FCC to declare that any social media that engages in editorial action is a publisher and not a platform, immediately exposing all of Big Tech to liquidation-level legal action as they gain secondary liability for every crime and tort committed where the platform was used in some way.”
Their exemption is in the law, not FCC regulation.
The FCC, and by extension the Executive, has no authority to change the law unilaterally.
He’s not changing the law. He’s simply directing the agency to acknowledge the reality of the situation, that Twitter is not a platform but a publisher due to its editorial activities.