If I was a cop, I'd be doing dive rolls everywhere... even routine traffic stops. There is no substitute for a good proactive dive roll when enforcing the law. People know better than to f*ck with an adept dive roller.
as opposed to now, where you just roll everywhere?
On topic-
it's worth noting that when the officer pulled his weapon, it was because someone ran up on his side while he had the girl down.
this same person had a hand reaching/near the hip, so it would be easy in that situation to assume that he's reaching for a weapon of some kind.
after the individual runs away, he holsters his gun again, and continues with what he was doing.
tl;dr
was he being a dick? yes
was he using excessive force up until that point? yes
do i think the gun drawing was warranted, and handled appropriately? maybe, but i'm not a cop.