I don't think my summary was unfair. I was only asked if there was evidence for persistent effects. There clearly is, even if just for adolescents.
It's also important to point out that for the adult-onset group they only looked at 1 year back. This doesn't preclude the possibility that longer periods as an adult find different results.
Your summary missed a critical piece, which is that it is just for adolescents.
I don't think, even within the marijuana community, that there is any debate that marijuana use in adolescents is harmful. I regularly see /r/trees comments telling teens to stop until they're at least 18 and their brain finishes developing.
It's also important to point out that for the adult-onset group they only looked at 1 year back. This doesn't preclude the possibility that longer periods as an adult find different results.