McGrath of Harlow said:

The yanks throwing rifles struck me as very clever but... The point about ceremonial parades and that is that what is happening is a ritualised version of something that actually has or at one time did have a military purpose. Juggling rifles is a circus trick.

Having once juggled rifles myself, perhaps I can explain. There are a number of different styles of doing the various necessary things with rifles. For ceremonial purposes, older and more elaborate 'changing of the guard' movements are often used. The moves McGrath objected to were probably from the Queen Anne Manuel of Arms. You ought to see some of the things the Russians do on ceremonial guard mounts.

Trivia note: It was the Duke of Wellington who banned the 'goose step' in the English army. Too many back injuries, he thought.