Well yes, you are right. But just the fact that something is difficult to overdose does not imply long-term safety of use. And as far as I know there are know connections between certain psychiatric issues and LSD usage. This is why I do not believe that "LSD is basically harmless".
It is harmless compared to many other substances, including aspirin and acetaminophen. Pretty much everything when taken in excessive quantities is harmful.
You're an idiot. Flashbacks are not a real thing. Pretty much every negative effect of LSD is exaggerated or based on biased reports by the government to justify making anything that gets you high illegal. An LSD 'flashback' is more like deja vu, like "Wow this is really similar to something I've experienced before", not like you just randomly go back into a full on trip. If you're schizophrenic you probably shouldn't take LSD, sure. But if you have heart palpitations you probably shouldn't drink Red Bull. People should be responsible for their own decisions, not you or the government or anyone else.
An idiot is "an intellectually disabled person, or someone who acts in a self-defeating or significantly counterproductive way". Does not seem to fit the definition.
How nice of the government to protect me from the minute possibility that a bad acid trip will give me PTSD. If only they cared as much about all the young kids they send over to the Middle East.