Why is medical marijuana more controversial than medical heroin?

Why do people make such a huge fuss over medical marijuana but not medical heroin? I've even heard politicians (who should be educated a little bit on all issues like this) say that there are "better" alternatives than marijuana but they have worse side effects, the risk of physical addiction, and a risk of overdose. It can't just be that the people are ignorant .

: http://alcoholdrugstreatment.info/why-is-medical-marijuana-more-controversial-than-medical-heroin