Self-contradictory

For example, if a chain-smoking teacher cautions a pupil for smoking, that warning is self-contradictory.

The conception of a noumenon, that is, of a thing which must be cogitated not as an object of sense, but as a thing in itself (solely through the pure understanding), is not self-contradictory, for we are not entitled to maintain that sensibility is the only possible mode of intuition.

The statement “We agree to disagree on everything” is self-contradictory.