GOD. I gave you a very specific example of when reagent tests can certainly do much for harm reduction: LSD vs nbomes/dox/bromodragonfly. You say we should be ' careful with what we take' . I'd say it's way more careful for someone taking LSD to reagent test using ehrlich than to not test at all, and this has nothing to do with 'guilt complex'.
You are still entitled to your opinion of course. Personally I feel reagents are definitely lacking, which is why I've been working on TLC. But I don't think reagents are completely useless, I think you probably say that from a place of having very little experience with reagents, and I think if you look at it carefully you see there are definitely clear exmaples where it can be useful. They are most definitely use by different international harm reduction organizations, while being conscious of their limits. Some organizations have access to other techniques and instruments but others don't and still make good use of just the reagents .
As for the synthetic cannabinoids, to be honest I have not researched much in this area. I know certain synthetic cannabinoids can be differentiated with different reagents, but I'm not sure if any of those cannabinoids is specifically less or more risky than others so I'm not sure how much the reagents would help appart from simply curiosity's sake. Personally I think harm reduction in this case would most likely be switching to cannabis instead of synthetic cannabinoids, but there are other contextual factors and preferences that need to be taken into account.
As for cannabis, GOD, do you have any source regarding your claims of "cold water wash" (what does that even do, cannabinoids are not soluble in water, makes no sense to me) and of 'oil' added to cannabinoids? I have looked plenty and didn't find much. In terms of oil the only publication I found mentions a couple of samples with some pine resin in Charras samples in italy. Certainly not as widespread as some people claim.
Also when you talk about 'western europe' , that is an innacurate generalization. Many of the main consuming countries in western europe like Spain and Netherlands do not smoke serbian weed, there is a local growing culture. In any case, what test from Serbian weed showed what pesticide in what amounts? Source please. Same for 'commercial hash made of broken LPs', got any source for that claim?
And as for your last question regarding safety of LSD vs research chemicals, I think obviously LSD being safe doesn't make other RCs safe. Several research chemicals are way more toxic than acid (including the ones present to substitute acid). But it may also be that other RCs are even safer than acid (not the nbomes/DOx/bromodragonfly, though).... It's a case by case thing.