Disappointed

I got a part-time job and have been worked for two weeks so far. I was in a bad mood because Dr. Zhong, our professor, transferred his anger to me today.
Dr Zhong was bothered by students who took credit less than 16 credits and they were in danger of being forced to discontinue schooling. Those students went to his office and asked him if there will be a remedy for that. Then Dr. Zhong asked a favor of me to stamp his name on all credit sheets. When it was done, I handed over those credit sheets.
A few minutes passed, he was out of his office and shut the door with a long face. “Done? Didn’t you check those sheets for me and pick up the sheets that were not up to 16 credits?” He said with an angry tone. “YOU DIDN’T NOT. You didn’t ask me to examine the contents. How dare you are to ask someone to help you without doing your duty previous!” I screamed inside, but still kept a smile on my face in order to pay my respect to him and show I was obedient.
Was it my fault? I don’t think so. Poor Dr. Zhong, he lost his temper and not only did he make himself but others sad,as well.
This is my first part-time job. By the way, I work for teaching staff. I didn’t have working experience before. However, I’m happy to get the job accidentally for it requires one person. Besides, I will learn the firsthand news than other students do at our department. No doubt, it’s a good job though it’s heavy.
“Dr. Zhong, I’m not a dog you yell to. If you were not satisfied with me, I would leave right away. Just tell me! I don’t care how much I make, I need to be in a good mood to enjoy whatever I do”
I was so disappointed. The part that I put in quotes above is what I want to say to him. But, I know…. I know it was not proper if I talked him back at that time.
Sorry, friends! This is not a piece of good news to share, but it did hurt me and made me uncomfortable. That’s something on my mind. (>_<) :-(