We often say here that an SO always gets an invite unless they have physically assaulted/harmed or stolen from the Bride and Groom/family member (or pose an outright threat to guests).  Tonight I was contemplating this rule and I wondered why verbal/emotional abuse gets a pass on this.  I don't think anyone here would disagree that verbal/emotional abuse is a real and incredibly harmful thing.  Many of us here have been in verbally/emotionally abusive relationships. Yet somehow, when there are individuals who are verbally abusive, our advice is to invite as a social unit, or not at all.  
I guess my (hypothetical) question is: If your family member or close friend had a SO who verbally/emotionally abused you (or FI), would it be okay not to invite them?  Why or why not?  Go!