What type of people were supporters of imperialism?

It tended to be the middle class people.

People who supported imperialism claimed that it was the natural progression of civilized countries and races to expand. Expansion in a way became a matter of race. Americans were part of the great Anglo-Saxon race, which means that, like their English cousins, they were of a superior race and destined for an empire of their own.
Hope this helps :))

Ending prohibition in oklahoma schools