He also said that he got annoyed when the police announced that there was a particularly potent batch of drugs on the streets at the time. His reasoning is that it only encourages drug users.
Also, experience of using drugs is no guarantee of safe drugs practise. If anything, it's the contrary. People become complacent in what they think they can handle, which spells trouble.
Also, drug purity can vary by region. You won't know about it in advance, but if you take drugs from a less tainted batch then you usually do, then you could well be taking a much higher dosage of the drug than your body is used to. Not good.
And finally, the most chilling part of all. He said that if you were to put some heroin on a table and say that this is the purest heroin on the market. You can take it, but knowing you will die. Many would still take it.