<human>: Condense the text into a few key points

This is a long-ish story and im on mobile so please excuse my errors. 
I recently started baking at a coffee shop and the guy who was training me was being friendly and bantering, then after I left he was going to the owner to complain about my lack of a filter. 

Supposedly he is extremely sensitive but he was mocking me and joking about me and with me all day and then talking to the boss after I left. The guy is very odd. 
 
The boss wants me to continue working with this guy but after the last shift I honestly cant. And he (the boss) keeps calling me, asking me if I would be comfortable working with him tomorrow. 

Now before you tell me that I should be more careful with what I say and maybe I should apologize, I have! And he never seems too offended.. But then I get talked to again, and its all piling up and making me feel like I cant open my mouth. 

I honestly dont think there is a place there for me. I just need help with wording my letter or resignation and maybe some help with how defeated im feeling. Should I have stayed? Am I doing the wrong thing?
<bot>: thinking about quitting a job because im working with an insufferable man child, need some advice on what to say/write.. Feeling really fed up and frustrated.