There's an old report (like from the 1990s) on this that put the DV rates at 40%. That's probably high but it's the source for a lot of the "cops beat their wives" claims.

A fundamental problem with cops is the thin blue line is very real. The rise of cameras on cops shows pretty clearly that a decent number of cops bend over backwards to protect their own. I find it pretty easy to believe that cops won't arrest their fellow officers on a DV call.

Police unions fight HARD to stop any sort of accountability or tracking of misbehavior of cops.

That's what the ACAB sentiment is about. It's not that all cops beat their wives or make up reasons to pull over minorities. It's that the ones who don't do that still cover for the ones who do.

That study is extremely misrepresented. It looked at household conflict rates, but the internet imagined that every act of violence was perpetrated by the officer, and not the spouse. In fact, the study found that the spouses of officers reported a higher rate of aggressive acts against their spouses, than officers did against their spouses.

The researchers also didn't conduct these studies on non-officers in the same location, in order to determine a baseline rate.

You also have the fact that "violent behavior" was not defined by the researches, so it left everyone to use their own personal definition. Maybe people thought violent behavior was yelling, or slamming doors. Is that domestic violence? Maybe, but I think when most people hear domestic violence they imagine a man beating up his wife.

And then there is the issue that these studies only involved a few hundred people from a specific location, like 40 years ago.