Racism.....

You don't get it, no-one gets it, but plenty of people do it. The Nazi's did it to the Jews and the Gypsies, Stalin did it to all sorts, the Sunnis do it the Shia and vice versa. Most of it will be a well ingrained national hatred for some long forgotten slight (the Jews killed our Lord; The Sunni's follow a false Prophet etc etc), but I suspect there is some inate human trait that causes us to be wary of someone who in not like 'us'.

Part of the problem is that stereotyping people, which ultimately leads to overt racism of the worst kind (discrimination, abuse, death), stems from some kernel of truth. Maybe a Jewish person did 'screw' someone on a business deal - so thereafter all Jews are dodgy. Even if 99.99% of the remaining Jews are perfect, we are all tarred with the brush; and it probably takes over 100 nice business deals with Jews to overcome the prejudice of that one dodgy deal.

Its human nature which is why it takes some much effort to stamp out racism.