Why don't more people see multiculturalism for the negative and divisive, anti-Western force it is?

It is not just American thing man, believe me. We are all facing this problem in all western countrys. We are outnumbered in our own homeland by people who come here and then try to make it into THEIR place which they left, If it is so great then why do not they GO BACK THERE and LEAVE US OUR SPACE?!?!?