The Vietnam War was a counterinsurgency that involved us in guerilla warfare that was similar, in some ways, to what we face in Afghanistan today. But the way the Vietnam War was conducted was considered to be immoral and unjust by many. Some of this has to do with the Soviet Union meddling in the domestic affairs of the United States (that is where all the money came from for all of these anti-war protests). It also had to do with countries like China and the Soviet Union secretly providing the Vietnamese with pretty serious weapons to fight the United States.
Keep in mind that you do not have to respond to each of the above bullets. Rather, this information is simply to provide some ideas on how to respond. As always, please feel free to ask questions.
Please remember to support your opinion with well thought out fact. Do not just state your opinion and leave it without giving the reasons why you think that way.