Arizona's new law to arrest/detain those who "look" like an illegal immigrant

Arizona's new law allowing police officers to stop those who look like illegal immigrants is laughable.  What exactly does an illegal immigrant look like and how does that person's looks, language, and demeanor differ from a legal immigrant?
What are we so afraid of that we have to waste time with stupid laws?  This is a law clearly directed at brown people as since as Robert Jensen argues "America is a white country"Jensen article.  Are we afraid that someone is going to take away our country like we took away theirs?
The absolute irony is that all of our border states were once part of Mexico before we purchased (wheeled and dealt) them.  So families had been living in those places for centuries and after the purchase, an arbitrary line was drawn to separate them into two countries with different rules, laws, and requirements.  Yet the cultures that existed had been the same for years.  Just because white Americans see a line that separates two countries at that border doesn't mean that the native people who live there see the same border.  Yes, you could argue that that border has now been there for at least 100 years, but if white Americans are any indication, you could also argue it's hard to teach an old dog new tricks.  Just for once, I'd like someone to look at a situation from a perspective other than his/her own narrow one.  To me the bottom line is this--the new law just legalizes racial profiling.