Is ethnic cleansing right? At any point by anyone?
Ethnic cleansing is never right. The problem is that sometimes it is effective. Especially in social groups which have irrational ideas about other groups, it can be effective in reducing tension and conflict. It can be effective in protecting people. And that might, just might, make it genuinely justifiable in some cases.
The ethnic cleansing of the Jews from the ME, for example, had a protective effect -- it protected the Jewish people and all their descendants from harm that might have come to them in the ME countries that would likely still be on-going today. The ethnic cleansing of the Jewish people from Yemen had a protective effect. The separation of India and Pakistan had a protective effect (fighting is largely contained to border areas if I understand correctly).
I don't believe it is morally correct to restrict Jewish settlements or remove Jewish settlements based on ethnicity. No matter how you color that one it remains nothing more than the argument "there can be no Jews in 'Palestine'" and that is a morally unacceptable position to take. Especially when it has yet to be determined where this 'Palestine' will be.
However, for Israel to say to its own people -- you can not build there, it is for your own safety. THAT might be justifiable.
This is a situation that Israel also faces. In the minds of many in Israel, including those in the government, it is getting harder and harder to justify the continued danger of having a hostile population live among them. (If the point of terrorism is to induce fear -- the Arab Muslim Palestinians have done a mighty fine job of it. Its just not having the intended results. Instead of causing the Israelis to capitulate, it is strengthening their resolve to ensure "Never Again" means just that.)
Then question then, for those who care to indulge me, is whether or not
it might be justified, for the safety of both the Jewish people and the Arab Palestinians, to separate them physically.