I had a hard time with Dean's speech to Kevin too. It just didn't seem earned. I believe Dean cares about him, but not to that extreme degree. It was so over the top that it felt more manipulative than touching to me, which could be bad writing or could be deliberate. Last week Dean used a big speech about his love for Sam as a means to betray him, so maybe his speech to Kevin is supposed to feel weird.

I enjoy being cited alongside Crowley on the subject of Kevin's mental state. :D