I suppose it depends on what you mean by "judge."
It is in my opinion totally fair for one country to think whatever they want about another's cultural practices. After all, we are all entitled to our opinion.
Now, do you mean to ask if it is fair for one nation to try to stop another's cultural practices? I would say yes again, as long as the country is not doing something like invading the other country.
For example, let's say we want to use our money or our policy to stop "female circumcision" in other countries. I think it is fine for us to do that as long as we are giving the country a choice -- you can stop that and get our aid or you can keep doing it and not get our aid.
There is no reason that one country should have to help another country do something the first country thinks is morally wrong. As long as you are not being violent, I think it's fine to judge and/or try to stop other countries from doing things we think are wrong.