Yes, Ball even said he wanted to explore a relationship where there was love, but required a lot of work on a consistent basis. My marriage is similar, so I certainly relate. Nobody could point at either one of us as blameless or to blame.

They both fed off of each other's insecurities and weaknesses, you can't really single one out as being this horrible person and the other a saint. However, I think Keith was more consistently in the wrong. I mean, Keith
was
definitely too angry and insensitive. Just as David was too needy and controlling, Keith had major anger problems he took out on David, wasn't comfortable discussing his feelings, and was generally almost impossible to please. They both got a lot better by the end of the series, but I think if either of them were to be called emotionally abusive, it'd be Keith. David, while OCD/controlling, still assumed the more subservient role in the relationship, while Keith unconsciously stepped up and dominated David, making him walk on eggshells much like Keith's own father did to him. But, just like real life, it's complicated and no one is either entirely good or bad.

I agree that Keith was a wonderful man. But he and David had a very symbiotic relationship. Look he was a cop and a lot of people go into that profession
precisely
because they want to save people. I agree that David could be needy and annoying at times, but he was well matched with Keith.

Never say never