The same reason speakers on Palestinian rights often can. While they may be on the right side of the issue, it's also very easy for closed discussion spaces to rapidly devolve into pretty viciously anti-semitic tropes.The roots of this behavior as well as the fear of this behavior lie in a logical fallacy called composition, which is spelled out at the Nizkor Project (a site on the history of the Holocaust):
> The first type of fallacy of Composition arises when a person reasons from the characteristics of individual members of a class or group to a conclusion regarding the characteristics of the entire class or group (taken as a whole). More formally, the "reasoning" would look something like this.
> Individual F things have characteristics A, B, C, etc.
> Therefore, the (whole) class of F things has characteristics A, B, C, etc.
http://www.nizkor.com/features/fallacies/composition.html
Just because the Israeli government is highly repressive towards the Palestinian population in the West Bank and Gaza, and treats non-Jews as second-class citizens within Israel proper, does not mean that all Jews around the world share this behavior. Similarly, just because some Arabs have carried out acts of terrorism does not mean most Arabs approve of terrorist attacks on civilian populations. These notions can certainly be extended to caste conflicts among Indian peoples.
For example, Jews and Muslims live side-by-side in New York City in relative peace and harmony, as do European and Arab descendants.
The reason for this is that the American tradition of strict separation of church and state prevents any one religious group (or ethnic class) from seizing political power and using that power to repress other groups. This is one American tradition that the rest of the world would be wise to embrace, if they wish to minimize such conflicts.