Most of those who care enough about immigration to write or speak about it, have already made up their minds about the issue. They will argue backwards. For instance, someone who wants to show that an earned legalization component to an immigration bill is a bad idea, will look for evidence to back up that point of view. On the other hand, those who believe it is a good solution will try to bolster that opinion. If we were being fair about an issue, we would listen to both sides of the argument and then decide what the ideal solution should be. Blanket Amnesty? Mass deportation? Getting the undocumented to self-deport? None of these solutions seem feasible. The brave Senators who are actually doing their jobs are trying to find a solution to a problem where virtually everyone believes the status quo is unacceptable.
One can find polls to back up almost any point of view. The validity of any poll depends on: sample size, randomness of the sample, the universe the sample was chosen from, how the questions were phrased, the collection method (phone call, mail, website etc.), and how the results were tabulated, among other factors. Lou Dobbs will cite polls that bolster his point of view and La Raza will cite others. As with most issues, the solution to the immigration problem lies somewhere between the extremes of the lying polls.