When certain words come back to haunt him, he claims he didn’t mean them. Retroactive sarcasm gives him plausible deniability — a way to make shameless statements without being held accountable for them. If Congress impeaches Trump for obstruction of justice, no doubt his lawyers will say that he obstructed justice sarcastically.
In his book Talk Is Cheap: Sarcasm, Alienation, and the Evolution of Language, Professor John Haiman describes this tactic as “a kind of self-protective and preemptive self-abasement, comparable to the submissive posture of dogs and wolves in the presence of the alpha male.” Implicit in every word Trump utters is a meta-message: “I don’t really stand by this; confronted by opposition I will cut and run… You thought I was serious? Ha ha!”
Other provocateurs use this same excuse. Milo Yiannopoulos claimed he “wasn’t being serious” when he said he couldn’t wait for “vigilante squads to start gunning journalists” just days before a gunman killed five journalists last year.