In the eyes of the law people can usually give consent while under the influence of drugs and alcohol (significant exceptions do apply, with the most common one being incapacitation).
So the position isn't extreme in the slightest. It's widely agreed upon to the point of being codified into law in a lot of places.
> There is absolutely no way I would consider consent someone gave me while they were on it valid in any sense.
Parent does not say anywhere that he/she is a therapist, this is the statement which seems extreme as it would criminalize all sex with people who are under the influence of MDMA.
The equality of states and setting thing matters too. People on MDMA love touching and socializing and if we're both on it, we both know what we're going into, so I'm content (in my sober state describing my high) saying I'd let a lot of that happen because it's fun for us. There are things you sort of assume and which you sort of innocuously chat about where you figure out if they're experienced. It's not strictly speaking consensual when you're both on the drug, but you're not wholly absent. Obviously you don't mess with someone's first time on it, you give them a safe way to be happy without escalating interactions. But if they're experienced, then you can both play.
Example A. My hypothetical partner and I are bored and we want to spice it up a little so we get some MDMA.
Example B. Your graduate advisor is bored, has a party where there’s lots of acid, and, oh, some MDMA too.
There’s no way in hell these situations are similar.
MDMA is a wonder drug and absolutely magical. I have loved using it. But I, for one, behave way differently on it. There is absolutely no way I would consider consent someone gave me while they were on it valid in any sense.