1) Define harm reduction
2) Give examples/treatments
3) Briefly explain the controversy
4) Thesis (last sentence of your introduction):
Option #1: Harm reduction should be an addiction treatment due to X, Y, and Z.
Option #2: Harm reduction should not be an addiction treatment due to X, Y, and Z.
Structure Example Body Paragraph X (using ‘should be’ as the thesis):
To begin, X is a reason why harm reduction should be an addiction treatment.
=> explain X
=> give examples of X
=> prove thesis (using X)
Thus, harm reduction should be an addiction treatment due to X.