When you do a lot for someone and they don't appreciate it and talk down to you it's VERY hard not to go off on them. I deal with that a lot with my job and there are days I want to punch a hole in the wall out of frustration. Thankfully I just picked up a punching bag at a yard sale for $10.
Did the mounting hardware come with the bag? Those things can be a pain to set up without a stout chain and a sturdy joist... and a strong assistant.