"Cocaine, for example, was among other things a topical anaesthetic"
"Has been used" is very different than saying it has a 'correct' use as a medicine and any other use is an 'abuse', isn't it?
"MDMA [Ecstacy] has been used in psychotherapy"
Very briefly, before it was outlawed. It was used to get people to open up to eachother and communicate in a state of euphoria. Its current use is for a very similar purpose, so branding one 'use' (because it was in a respectable context) and the other 'abuse' (because it is in a recreational context and you don't like the word) is rather hypocritical.
"I bet those who synthesised it never imagined it would end up being the stimulant of choice of monged-out crowds"
That is a bet you will lose, I am afraid. Meet Alexander Shulgin, the scientist who first synthesized MDMA (Ecstacy) in 1976, and who continues to use it very recreationally, partying with his friends in his house.
Shulgin prefers classical music to go with his MDMA rather than techno. Does that make his recreational MDMA consumption "use" or "abuse"?