That is the law in Florida, as it is in many other states. The responding officers don't have any choice. An arrest must be made. I find it VERY difficult to believe that not a single officer who was on the scene early Friday morning didn't suspect a DV situation then. FHP has some explaining to do, IMHO.
I agree with you, however, the situation is probably similar to the Ft Hood nutty psychiatrist case. Had proper action been taken, the public safety would have been defended while the PC police would have hung out legitimate authority to dry. The same people here who assert one should never talk to legitimate authority, would then use the law enforcement to further justify their perspective that one should not work with legitimate authority.
In essence, rejecting legitimate authority in favor of independent means is merely a rebellion for recognizing legitimate authority.
Compare the Mob and how communities allow it to be established without formal public recognition. It is simply ignored and not reported to legitimate authority, thereby giving it more power to further corrupt society.
The same happens here by refusing to discriminate legitimate behavior from illegitimate behavior, then encouraging silence.