Good point about Flynn. The threat of impoverishment and/or imprisonment for a contrived legal infraction would probably make most people compliant with the threat maker's wishes.
Contrived how? He was fired from his position by the president
because he lied to Pence about his contacts with Russians, but somehow we find it doubtful or some kind of unimportant process crime when he lied (again) to an investigator.
Trump is being a bit disingenuous here. He's saying Comey should be in jail for the same things, when he specifically asked previously if Comey could 'let it go' with Flynn. Had the Flynn inquiry been dropped, do you thing Comey would still be FBI Director? Of course not.