I think it depends on amount of whatever ingested, and intention for it. Being incoherent is pointless and probably reflects a dysfunctional intention that would be better addressed directly.

But ingesting just enough to decrease anxiety and inhibition on an occasional basis isn't necessarily a waste of therapy time, disrespectful (I would not do this without prior discussion), nor dysfunctional. Let's remember that some of the most enthusiastic proponents (and researchers) of LSD were psych practitioners. I think some generational thinking has been overly influenced by the "war on drugs."