I have used a big word in the title, a word that is used in philosophy of knowledge (epistemology). It means no common measure available between two things to compare and contrast. When you have to compare between two scientific theories, some philosophers used to speak of the the term incommensurable as they belong to different world-views. This theory was not so well accepted; many of the so-called competing scientific world-views have many things in common. So there is option to compare and contrast. Science may have forgotten this term, but it is implicitly present in other fields.
Today we live in a world which is very much diverse. We have people from different and varied cultures, nationalities, religions living together. Does it mean in the name of accepting diversity, we should allow anything. This is a serious question being raised? Occasionally we could say people belong to diverse world-views and it is difficult to judge whether something should be allowed or not? Can we allow anything to go in the name of diversity and incommensurability between the diversities?
I am nobody to dictate the terms of judgments. But what could help us in dictating terms of judgement. Some helpful items may be
Human Rights declaration. The rights of the human being shouldn’t be violated in the name of religious/cultural/national practices. I am sure consensus is not easily available here too, but dialogue should take place.
National laws can be another help. But when they are outdated, even such laws need to be challenged
Religious and cultural taboos and systems are very important human social systems. But they shouldn’t be override the basic freedom of an individual.
When there is need to make such judgments, the identity that should be focussed is not the divisive identity, but a common identity. For eg, when there is a riot in the name of religion, the identity that we should appeal to is not just the religious identity, but a common identity (human/Indian/same culture etc).
We should fight attempts to make diverse religions/cultures/nations incommensurable. Although their world-views are different, still there are some things common among them. We also shouldn’t go to the other extreme of making everybody one, throwing out all diversity.
We shouldn’t opt for the extremes — sameness or diversity, but a difficult marriage of sameness & diversity.