It is just as likely that the situation would have resolved itself peacefully and without further incident...
That is commonly known as Monday morning quarterbacking.
Officers engage in lots of training because in any given moment reaction occurs rather than analysis.
The end officers want is resolution without injury if possible.
Had the then present teenagers and full-grown adults (it was not just teenagers present in the video!) acted promptly to police request to either sit down on the ground or leave we'd have not seen the bikini gal tossed to the ground and we'd have not seen an officer draw his weapon on multiple males aggressively entering his personal space from behind.
Law enforcement officers are not baby sitters. We pay them to deal with messy stuff, and to keep themselves and the public safe. When we call the police via 911 we are not asking for someone to come counsel teenagers; we are asking someone (in this case) to come intervene in a dangerous situation that involves a whole lot of individuals, any one of which could have a concealed weapon and often do have one.