The question deserves an answer. Several answers, really.
The first is that different people read information with different levels of skill and understanding. Auto accidents, for instance: "Fifty-two percent reported they were 5 miles or less from home, and an astounding 77 percent reported they were within 15 miles of home." Some people read this and decide it is much safer to be on the highway in another state than to be in your own neighborhood. Other people realize that they do most of their driving close to home. Even if they are driving 50 miles away, they have to pass through the 'statistical zone of death' to get there. The statistic is meaningless.
Not only is there skill in reading the data, there are very intelligent people who filter information through very different paradigms: The war in Iraq has cost more American lives than any war the under thirty set can remember. It is a huge tragedy and the bloodbath of their lives. A more historical perspective will compare it to single days or battles in other wars and the data, the raw number, will have different meaning and impact.
Then there are sources of information- anyone with access to TV, radio, papers and the internet have access to the information that everyone else does... but they don't access it the same way. No matter how much you deny it, consciously or unconsciously you are cherry-picking your sources to agree with your world view. I can find sources that say global warming is happening and is caused by fuel emissions. I can also find articles from many of the same organization from the seventies saying that the same emissions were bringing on the next Ice Age.
(And these two sources of difference, paradigm and choice of sources can blend such that if my primary source on Iraq are e-mails from soldiers there
But possibly the biggest is that people who live different lives and are exposed to different populations see different results from the same things.
Why are college professors generally for relaxed immigration laws and for government aid and cops, in general are against both?
It's because we see different outcomes. The college professor sees the students who worked hard, took advantage of what was offered and used it to create good and productive lives. Sometimes against great odds and defeating incredibly negative circumstances. They see the good that the programs do.
The cops deal, every day, with the people who took advantage of what was offered to increase their ability to harm or to evade responsibility for their actions.
The programs that allow a young man from Mexico who illegally crossed the border to find a job, get health care for his children, become an asset to his community, pay taxes and have children who go to colleges and make America stronger are exactly the same programs that allow cartels of drug dealers to pack their organizations with relatives from the home country and rule through fear and traditions that were imported right along with them.
The programs that allow a struggling single mother to care for her children and keep them fed and get them to school and give them a chance at a life are the exact same program that enables teen age boys to have contests on who can father the most illegitimate children before graduating from high school, and do so with absolutely no responsibility or penalties.
This is important. Sometimes the argument arises because the friend has a colleague who really made it in life with a little help paid for by the government... and you have either just delivered or just buried a baby addicted two two drugs and underweight with no functioning parent and that, the birth or the burial, were also paid for by the government.