I understand what you're saying. At the same time, where do you personally draw the line for what is psychoactive and what isn't? I generally don't think of alcohol as psychoactive in the same sense as LSD or psilocybin. Mood altering might be a better term, but at the same time, I know I'm often more irritable if I'm hungry. Your parent isn't arguing that people need alcohol to feel a connection, only that it might have some benefit (and not even that it is only beneficial: they acknowledge it has downsides).
What we eat, drink, what medications we're taking, how much we exercise--a whole host of factors play into how we experience and react. Do you feel the same way if I know I should generally eat something before going out? Honest question. I'm not sure where I draw the line, though I admit to wanting to.
Lsd and ethyl alcohol only have different effects, it's the dose that determines how extreme the change is.
Is this not a proven fact, though? I'm curious as to why you phrase it as a suspicion when, for example, we know very well that alcohol/caffeine/sugar affect your mood and cognitive abilities in the short term. Did you perhaps mean that you suspect there are other effective chemicals which we assume do not impact mood/cognition?