He was aggressive, waving a lit cigarette around. He was swearing and abusive, He mentioned his service as a threat rather than a statement " I'm a US soldier man, now you know who your talking yo!"
In UK I would have issued a public order warning for the first incidence of swearing, and then nicked him for the second. A slap or a push are routinely used to prevent a situation escalating. It comes under the 'ways and means act' and whilst the public watching a video in the cold light of day, may draw their own inferences, the way the officer reactedis a vital and oft usedtechnique.
Could the LEO have dealt with thisin a different way? Sure, maybe he could have talked him down, been more empathetic? Quite possibly, but it was his call at the time and resulted in a potentially aggressive little twerp being subdued and defused the the situation expeditiously.