Why some sikh youth gets brainwashed for hating islam and muslims , at the behest of hindu fundies (RSS )?

It's not just Sikh youth being brainwashed. People of all races and cultures from all countries and walks of life are brainwashed into hating different groups of people. It's sad how others can hate someone else just because they believe in something different than you. I've never read about a religion that found hate to be acceptable.