The two main issues were the civil rights struggle and the Vietnam war
The civil rights struggle was important for SDS activism because they supported equal rights and democracy and wanted to end things like segregation and inequality. They also supported a reduction in inequality between the rich and the poor which was also a big problem in the civil rights fight.
The Vietnam war activism was important too because they believed that the United States had no rights to interfere in the war and that American people were dying in the war as soldiers in a war that had nothing to do with the well-being of the people. They organized numerous protests against American participation in the war.
