One doesn't need to think "all drugs are the same" to spot the obvious argument here: psilocybin, although not considered to be addictive, has far more dramatic side effects than nicotine.
I don't see how that's an obvious argument either. Psilocybin isn't being used here as a substitute for nicotine so it shouldn't be compared to it as such.
It's being administered once as part of an intensive CBT program. MAPS et al have done studies that have shown psilocybin and other hallucinogenic substances can accelerate change in people's thought processes. Addiction is one of many possible uses for these substances, administered in a controlled environment under medical supervision and guidance.
