I can completely understand! I spent quite a bit of time in customer service jobs! One thing I noticed over the years was that for the most part feelings of anger/frustration generally turned into pity for people like that. I couldn't imagine waking up everyday and just view everything as being negative, out to get them, etc and having any sense of what I consider 'a life.'

Honestly, I commend you for still putting out positivity and niceness towards him! It's not always an easy thing to do, and many people never even think to try.