Hence it's important to get people to stop seeing opposition to legalisation of these drugs as "obvious", because opposing legalisation of these drugs is extremely irrational.

Current laws on this are immoral and deeply harmful. The vast majority of drugs should be fully legalised and regulated, not decriminalised. The only reasonable exceptions are possibly things like fentanyl and "synthetic cannabis" variants that few people use because they want just those drugs but because of poor availability of safer drugs.

Any evidence-based drugs policy would involve full legalisation of most drugs - there's simply nothing that suggests the current laws achieve their claimed intent, and plenty that demonstrate they are causing massive harm both to addicts and to victims of related crime.