Van-Tramp, wow... I'm glad you weren't the one the cops decided to "convict" in the moment, but it could easily have gone that way if they decided to believe her, or to interpret events in a way that looked bad for you--heck, even if one of them had an emotional response of protectiveness toward her. And, as you point out, even though she was wrong in that case, she really wasn't a threat, and nobody at the house really needed to be arrested or persecuted by the system.
In any case, it points up what most of us with some life experience, including you I'm sure, have sadly concluded: The law is not necessarily what's right or moral or noble. It's what some people in the position of power and influence--and for a mixture of reasons, smart and stupid, noble and self-interested--have decided should be the law. And, at its best, the law is very unwieldy, and in many cases will be applied indiscriminately...and therefore unjustly.
And while there are many wonderful women who would never initiate violence or unfairly call the police on their man, I certainly can't blame you for being wary of any further live-in domestic partners. The "do-gooders" in advocacy groups and legislatures have made marriage or live-in mating, and parenting, into very hazardous endeavors where one can be easily accused of abuse, and one's life ruined, very quickly.
'Glad you ducked that one.
GP