Bayonet training serves a purpose. It breaks down certain barriers that society has built up that are incompatible with being an infantry soldier. The likeliehood of a bayonet charge is pretty slim but the lessons learned while executing the training is still valuable. At the same time, teaching knife fighting, grappling, and hand to hand combat seems equally valuable to me. Marksmanship training, MOUT training, and convoy ops training seems like the most important training a soldier could receive these days however, especially for grunts.
There are fewer motivating and less countered comments than having to give the order, Fix Bayonets! (Of course, when it is given, everybody in the trenches knows what is next.)