I thought I read that the arresting officer was a latino.
As you would expect in a city like Cambridge, the police department is a very diverse group. And given the liberal mindset which created this whole situation, group identity matters. There were white, latino and African American officers present at the arrest. Knowing Cambridge I wouldn't be surprised if there was also an officer present who was GLB or T - no doubt the city has ensured equal representation for every group on the police force.
And knowing Cambridge, it is entirely possible that every person present - from the police officers to the neighbors - voted for Obama, and is a liberal Democrat.
Claiming that the police in Cambridge are racists is just silly.