Morons full of oxygen?
Webster defines oxymoron as a contradiction. Usage is usually humorous. ie. Military Intelligence, common sense, honest politician..
Oxymorons are not logical. An honest politician is not a contradiction in terms. A real politician is actually an honest a politician. That is, he/she is everything a politician is supposed to bea negotiator, a compromiser, a puppet of special interest groups, a liar, a cheat, a bribe-taker, a power abuser, a privileged class...
Honest politician is not a contradiction in terms but a contradiction in standards. We hire the garbage collector* but don't expect him to smell as sweet as a babysitter. Conversely, we don't expect the babysitter to smell like a garbage collector.
Therefore, why do we select a politician and expect him to be statesmanlike, morally correct (whatever that is), humble, and all the other standards of behavior that we ourselves claim to esteem but don't practice either. Therein lies the irrationality and contradiction.
A baseball player is hired to win games, not to be a hero to our children. What's "wrong" with his gambling? Gambling income is taxable by IRS, so it must be legal. What's wrong with him throwing a game so he can win his bet against his own team?
Cheating is smart, unless you're caught. Insider trading and stock manipulation is admired, even after the villains are "caught".
*pc term: environmental engineer?
See also cliches