If one athlete beats another to the line and that they taunted the loser didn't impact the result then the result should stand. DQing the taunter would be like taking away a touchdown for someone turning around and backing into the end zone, or (if it's after the finish) getting in someone's face after posterizing them with a dunk. We have penalties for those, but neither negate the result that we all just witnessed on the field.
The appropriate punishment would be forward-looking--a ban from the rest of the current and/or future meets in the relevant circuit/league--and in the case of professional athletes, financial--a fine--but wouldn't alter the outcome of something that had already happened. This silly moral puritanism is just another example of Athletics shooting itself in the foot by putting too much power in the hands of stick-in-the-mud officials.