Lilisdad and Edward429451, have hit the nail on the head.
The immediate fault lies with the individual officer, who while investigating the incident, could not or would not tolerate any behavior that was not completely subservient.
The more problematic fault lies with the administration that did indeed train this officer to expect such behavior and to retaliate if it was not given. (source? How do you know that's the way he was trained?)
In such zeal to decry this incident and to denounce this officer in particular, note should be given that not all police act in this manner.
Further, note should be given that we don't know all the facts. The paper has not printed anything more than what will sell papers. The paper has not released to the public any more of the video than a small snippit, that tends to support their story. We don't know what the officer said when he first boarded the bus. The video we were allowed to view, doesn't show this. Nor does it show what happens immediately following the "grab" by the officer, the handcuffing, nor the "lecture."
If I was on a jury and shown nothing more than this small portion of the tape, I simply could not conclude anything more than an officer seemingly taking a suspect into custody. The audio portion is poor, plus the voiceover by the announcer cuts out most of what was said. As a juror however, I would have to have viewed the entire tape, and not that snippet shown by the news. Else it all boils down to, "he said, she said."
To be sure, the school reviewed the entire video and found no fault with the girl. This seems to substantiate the allegations of officer misconduct. That gives some credibility to the charges against the officer. Yet again, a portion of any blame, to my mind,
would be the training the officer received and the administration that approved this training (again, not in evidence)... But that's just my opinion, based upon interaction with police in my area. YMMV
To sum then: Blame the individual, but don't blame the entire group.
As an aside: LEO: Singular. LEOs: Plural. LEO's: Contraction, singular possessive; LEO has. (damnable English language...)
As a further aside: Yes, this was an investigation.