I don't know that I'd say they're usually the instigator, but I will grant that they are probably half the time. My husband's fat ex used to occasionally hit and throw things at him, along with the near-constant verbal abuse. The only time he ever physically retaliated was the night she came after him with a knife; he head-butted her (he didn't have a hand free, since he was using them both to hold her off), and she went down like a stone. It really upset him to have to do that, but it's not like she gave him a choice.