Pushing the fat man is the wrong choice because it forces fat men everywhere to constantly be on the lookout for consequentialists, and causes moral hazard by encouraging lax safety around railroads. Consequentialism is only indisputably the correct morality when everybody is perfectly rational and everybody has the same goals. In reality people have differing terminal goals and perfect rationality is impossible because of limited computational ability. Deontology is superior because it is far more predictable. Nobody has to waste brain cycles on avoiding being a convenient victim for some dubious "greater good".