Exactly, I completely agree, it's a very silly thought! What makes drug use different from my example that people aren't able to have an informed opinion on it when they're involved?

It's like saying rapists are too close to rape and therefore their opinions on rape legislation are skewed.

Drug users are not the victims

Oops you're absolutely right. It's like saying drivers have skewed opinions on driving legislation because they're to close to the subject matter.