Why do I keep going back to a relationship that I know is bad for me?

It sounds like, while you are aware that it is not a good relationship to be in, there is a part of you that is more fearful about the unknown than what you are dealing with. The phrase "the devil you know" comes to mind. It also sounds like you go back/stay because there is something he does that makes you think he is going to change.  Based on your question, I would guess that there  is also an element of you believing that this is the type of love you deserve. It also sounds like, despite your family and friends dislike of this person, you might be trying to prove that you are able to change this person from who they are to who you would like them to be. 

I would be interested to know what your past romantic relationships looked like, if you had additional romantic relationships. 

I would be interested to know more about your childhood and what that looked like as I believe that a lot of what we do as adults is shaped by our early childhood experiences. 

In terms of the verbal abuse, it seems that you are justifying this type of abuse because it is not yet physical.  It is much easier to accept verbal abuse rather than physical abuse because, most of the time, people can't see the verbal abuse.  

I would suggest connecting with an advocacy group to see if they have resources to help you move on from this relationship, if that is what you want to do.  There are advocacy groups all over that specialize in helping survivors of intimate partner violence.  They would be the experts in helping you with moving on.  

I would like you to reflect on the WHY you continue to go back to him.  I would suggest thinking in terms of how does it serve you to return to him.  Is there a honeymoon phase where things are seemingly better? I would also suggest free writing some of the thoughts that come to you when you are thinking about this so that you could go back and reflect on what you put on paper.