Why? Society doesn’t owe you acceptance for your personal choices. For the vast majority of people, smoking marijuana is an anti-social choice that makes them a less productive member of society. Why should anyone have something other than a negative opinion of such a choice?
"You judged someone on a separate occasion, so you can't object to judging people now" would be tu quoque. What I actually did was point out the internal contradiction in your stated position.
I've said a total of four sentences on the matter, none of which hinted at its importance or lack thereof to me, so it's interesting that you've come to that conclusion. Either way, my internal motivations are a non sequitur. You are continuing to take a self-contradictory position by stating that a certain behavior, namely judgment, is not "ok", which constitutes a judgment. You have offered no defense of doing so. Should I conclude that you simply believe that oxymoronic positions can in fact be correct?
No it's not. Judging people is extremely important in order to enforce social conformity and norms. It's how we as social animals maintain civilization.