I understand your thinking that people should be safe with what they put in there body, and they should not take contaminated drugs, and this and that etc....I think the same way, I agree with you....
...but, thats not how the real world works....your style of thinking and reasoning is too utopian. Life isnt like that....there ARE contaminated drugs all over the place and people are injecting them all the time. And most drug addicts wouldnt give a penny for a micron filter because they would rather buy more drugs.....And since this is the way the real world is...it reduces harm too tell these people that cooking your drugs before injecting them can kill alot of bacteria....it may not be an ideal situation, and maybe these people should be using micron filters and injecting drugs they are 100% sure are not contaminated, but it simply doesnt work that way.
As long as addicts are injecting drugs that might be contaminated(and probably are) I think its a good idea to tell them ways to reduce harm.
Along with telling people to inject only after using a micron filter, and only use sterile equipment, and only use a needle once, etc....I will also tell them that if they choose not to listen to all of that advice, atleast cook your heroin, or your meth before injecting it so that some bacteria can be killed....reducing the probable harm for that person.