Why were the colonists upset about the stamp act

Let's first understand the other side of the stamp act to fully understand the conflict between the American colonists and Britain...

Britain had helped America out in the French and Indian war, which they won. After the war, they were in serious debt, and since they had helped the colonists out, they thought it was only fair that they helped pay back the taxes. (They also taxed their country to help with the debt). 

The colonists didn't like the tax for one main, big reason. This was that the colonists didn't think they should be taxed if they had no say in it. "No taxation without representation," they would often say. The colonists believed that Britain should not put taxes on them, such as the Stamp Act, without the colonists getting representatives in the British Parliament. 

Thank for the opportunity to answer your question and I hope I helped! If you thought my answer was detailed and helped you with your homework, I would ask you to please nominate me for the brainliest answer! Thank you! :)