I never said that simply disagreeing with Julia was the abuse.
For example, Barn's abuse of not only Julia but Willie as well often took the form of belittling not only the disagreeing person's opinion, but the person him/herself. Barn would often resort to psychological abuse by insulting Julia's attitudes, beliefs and/or manner when it was impossible for him to actually competently argue against her point because her view was quite obviously the clear and rational one. In Willie's case Barn would most often resort to manipulation and intimidation to get his way. And his psychological abuse of those around him continued to be Barn favorite M.O. for getting his way whether he was a vampire or human. Completely disregarding others' warnings was often what got Barn into more trouble than he and/or they might have already been in.
Also, quite sadly, coming to care for someone and abusing them, whether it be physically or psychologically, aren't mutually exclusive.