I think all judging is not only permissible - it's essential... it's how we make sense of events (and people) and measure them against others we have experienced so that we can develop an appropriate response to them.
Our judgements change over time as we gain more life experience.
I think the issue is sharing your judgements or acting on them when you haven't had enough life experience to make the response an appropriate one. Sometimes it is important to reserve our opinions or actions when we know that we don't have enough life experience to make an informed decision. Not passing judgement is also a judgement call.
Unfortunately, many times people don't recognise when to, and when not to.
If you're passing judgement on someone for making an erroneous judgement about someone else, it might be a good idea to step back and consider whether the person making the first judgement just needs a bit of additional life experience. Education all the way, I say!