So tell me, immigration opponents, what's the big deal?

Would somebody please educate me?

Reading through the great posts at Rep. Pena's blog and the comments from Wednesday's Grits post, I've been wondering: The main, non-racist source of opposition I hear toward illegal immigration is that, when people cross the border illegally, they may cut rancher's fences or vandalize property. From a public policy perspective, both of those are de minimus problems compared to the benefits to tens of thousands of business and households that rely on hundreds of thousands of illegal Mexican laborers. Plus, those negative side effects are purely consequences of immigration's illegal status, not inherent problems with immigration.

Otherwise, besides those with overtly racist motives, the main criticism seems to be that immigration is "illegal" and therefore immigrants are all "criminals." But those laws against immigration are national choices, and if the consequences of our choices become too dear -- if the detriments outweigh the benefits -- then they could be easily changed to "decriminalize" that segment of the workforce.

So besides one's punitive attitude toward any lawbreaker -- let's put that aside for purposes of this discussion -- can somebody tell me, with the U.S. unemployment at 5%, what is the big harm from immigration, illegal or otherwise, that we're trying to prevent? Don't we need more workers paying to keep Social Security and Medicare solvent? What's the big deal? And does any suffering that results from immigration outweigh these harms from its illegality:

• ranchers woes, cut fences and vandalism from using non-official crossings,
  
• inability of law enforcement to locate witnesses or crime suspects because of a lack of documentation, even home addresses, for immigrants,
• creation of the ruthless coyote industry,
  
• establishes routes, masks movements of real criminals, drug runners, etc.,
• creates a homeland security hazard in event of bioterrorism attack, etc., or any catastrophe where evacuation is required, since authorities don't have home addresses for hundreds of thousands of people,
• victimization of immigrants by employers, criminals, coyotes, etc.,
• creation of a class of criminals (like the confidential informants in the Dallas "fake drug" scandal) who are less likely to be targeted by law enforcement because they mainly prey on undocumented immigrants,
• heightened indigent care burden on local public hospitals and emergency rooms because of inability to qualify for Medicaid and CHIP,
• creation of categories of labor with no recourse to enforce state and federal labor laws, and
  
• overwhelmingly wasted federal law enforcement resources (immigration cases are now 1/3 of the federal total, more than any other type)?

Those are just a few off the top of my head. Maybe some commenters can think of other negative consequences from the choice of making immigration illegal. Or maybe somebody can explain to me the terrible harm that's befallen this country without me knowing it based on the presence of a few more people with brown skin?

Opponents of legal immigration, please tell me, what part of this problem wouldn't be made better if nearly all immigrants from Mexico entered the border at legal crossings, were given identification that included a description, thumbprint and home address (e.g., a DPS drivers license or ID card), and were allowed to work legally, pay taxes, and find recourse under the labor laws? In what way would that be worse than the status quo?

Texas used to be part of Mexico. Our state is home to lots of folks who moved here from there, and their kids, and their grandkids. I think we're better off for it. For the life of me, I just don't get the complaint.