<human>: Tonight after work as a karaoke dj, I shut down my system, turned off lights, and went up to the bar to wait for patrons to leave. All employees usually hang out after the door is locked, doing closing work, chatting, hanging out. We're all really good friends. 

Lately one of the bartenders has been really achey and sore, so I would put up all the bar stools on the karaoke side of the bar. (About 40 stools) tonight in was exhausted and told him I would do it, but I was really tired tonight so I was going to hold off for a little bit. 

We got a call from my boss saying he was stopping by... so I jokingly said, "oh good... he can put up stools!" Then the bartender said "I have you put those up for a reason." 
"What? Why?" 
"Excercise. It's something. I'm on your side here don't get pissed off" 

Here's my problem..  it hurt my feelings.. a lot. But I'm not sure WHY. he's right... that's a simple Excercise that I can do. but I was just filled with so much hurt about it. I just need help figuring this out. Am I justified in being hurt by this?

Can you summarize the given text in a few sentences?
<bot>: coworker had me do extra work just because I need excercise. Don't know if my feeling hurt/angry is justified.