Why do a lot of Americans hate mexicans?

I don't get it why there's so much hatred to these people. I can understand that Americans think illegals are getting rights when they shouldn't be because their "illegal aliens, criminals". but it doesn't mean you have to rat them out to immigration right? Not all illegals are bad, most families come here to find a new life especially for their kids, you would be surprised of how many of them actually want to succeed in life(how would I know? I'm Mexican but of course.) this is coming from some1 who actuall knows both sides of the story. I mean America would be in an even worse place than it is now without mexians, no American wants the job of a feild, and farm worker with low wages & the not so greatest conditions. How would you get so much vegitables & fruits,dairy,& meats without the work of so many people that will do anything for even the lowest amount of $ I'm sure you wouldn't want to work there now would u? Another is sometimes I feel that Americans just simply don't like mexicans. You hear a lot now that some are turned in to immigration or some were beaten to death by a group of people :P If u think about it when these people called immigration todeport these families think of the lifes they could of ruined, not all deported mex. come back some just stay back n mex. anyways those families could hav had dreams here n America. And it's really hard for illegals now a days to become legall, they have to wait a ridicoulis amount of years, & some just dnt have that time, that's why they come here illegally, cause they hav no other options. my point im tying to make here is, is it just hatred & racism that Americans just dnt like mexicans? or s it the whole "economic,rights thing" ? tell me your opinions