I think that the question might be more along the lines of whether it is inevitable. The idea of judgment is something that is present within all human beings. This would apply to nations. The idea here would be that the assertion of judgment should not come at the cost of another nation's right to be left alone. If a nation's judgment comes at the cost of another's state of sovereignty, then problems might result. It is almost morally impossible to ask nations and people to not have any judgment. If we move into that realm, then the ability to speak out is almost entirely negated. For example, the idea of not speaking out in judgment against the practices of Hitler or those commmitting genocide in Darfur, or against the civil war in Rwanda, or against Nicaraguan death squads is very close to giving moral permission to these crimes. Nations do have to be able to form and articulate judgmnets, and one can only hope that these do not bring greater conflict, but if a nation believes fervently that the cultural practices of another nation offends sensibilities, I feel that conflict is fairly inevitable.
My opinion on judging the cultural practices of foreign countries: I am not an anthropologist, but I would say "not". I lived in northeastern Asia for five years. The first year I was there, I hated it because they didn't do "it" the way we do "it" back home. After getting used to the way they do "it", I enjoyed my stay there very much. There are things about their culture that are superior to our culture. And there are things about their culture that are inferior to our culture. But those things work for them; they have evolved their cultural practices over thousands of years (just like most cultures). What they have is the distillation of hundreds of generations of experience. It works for them; it is not for us to judge it.
I believe that human nature stands in the way of being unbiased towards another country's cultures, especially if they are very different from our own. Human nature determines how we think, feel, and behave. If another country has practices that are are different from our own it is merely human nature that causes us to frown upon that or wish it to be changed.
Now, the question is whether this fair or not. People should be open minded when it comes to judging others. If a country is following practices that they have followed for hundreds of year then I think that it is only respectful to not interfere with that practice. On the other hand, if it is a practice that harms others then something needs to be done about it.
It is virtually impossible not to pass judgement on countries whose cultural differences are unlike our own. I see nothing wrong with developing opinions about the differences of various cultures, but when one country tries to take action against another for this reason, then the outlook becomes more muddled. Most American women find the restrictive dress of women in Islamic countries dehumanizing; however, fundamentalist Islamic cultures must consider the dress of Western women quite risque by comparision. Past ethnic cleansing in Africa and Eastern Europe seems outrageous to Americans, but the U.S.'s own actions in Iraq and Afghanistan probably does not sit well in other parts of the world. The eating habits in one part of the world may seem unusual in another, and vice versa. Personal judgements are to be expected, but open-minded individuals will usually not try to enforce their own standards on others. If and when this happens, then your question becomes a much more serious matter.
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.
The act of judging can be of different types, and the fairness of appropriateness of judging practices of another culture will very much depend on the nature of judging. When the judgement is bases on objective study of the practices followed by people of other cultures, and understanding the reasons and impacts of such practices dispassionately, better understanding between people of different cultures is created. It also enables people to learn from others and improve their own culture. It also enables people to modify their behavior appropriately while dealing with people of different culture. Judgment of this kind is not only appropriate and fair, it is very useful and desirable.
Unfortunately many a times we make prejudiced value judgments about other cultures without objective knowledge of what the exact cultural practices are, or how these are suited to the particular situations faced in different environments. Often in such cases people have an exaggerated views of the actual practices. Usually this leads to people often kooking down upon other cultures. This really bad as it creates disharmony and conflict among people of different cultural background. Some times people tend to look down about their own culture. This is also equally harmful.