Please try to think this through HONESTLY for a moment -- setting aside the storyline you've been fed by the conservative media.
Obviously, there's a reason we ID people who buy beer. The cost/benefit analysis weighs in favor of it. The "cost" is minimal -- if some people don't have ID and therefore don't buy beer even though they'd otherwise be eligible to do so, it's no great loss to them or to the country. In fact, you could argue that it's a gain. Meanwhile, the benefit of dissuading the underage from buying beer is arguably quite significant, in the form of cutting down on alcohol abuse among those too young to know better. We know that without drinker ID rules there will be a significant amount of increased drinking among minors, and we know that this will literally be a deadly thing for many of them.
Now, look at voter ID in the same cost/benefit way.
What are the costs of voter ID rules? The costs are that you'll dissuade a number of eligible citizens from voting. A small but significant number of eligible people don't have sufficient ID, and some additional number who do have sufficient ID won't happen to have it on them when they show up to vote. If these people were randomly distributed, demographically, it wouldn't be a high cost to the society, since it would be unlikely to sway any election outcome -- you'd have a couple thousand less people voting one way and a couple thousand less voting the other, mostly canceling each other out, with only an infinitesimal chance that the overall election result would be changed. But we KNOW these people aren't randomly distributed, demographically. We know they're more likely to be young, urban, minorities, civilians, and poor, for example, Those groups all have well-understood tendencies to skew in a particular direction, politically.... and that, I'm sure you understand, is why the Republicans like the idea of a voting rule that cuts down on their numbers. It's the exact same reason racists once liked poll taxes and poll tests -- they knew the disproportionate impact would be an electoral advantage for their side, even if it was superficially neutral. Significantly, Republicans are not dying to reform absentee ballots, despite the huge opportunity for fraud (no way to tell who actually casts the ballot), because absentee ballots tend to skew Republican. It's simply an attempt to sway results.
Because of this demographic skewing, the phenomenon won't mostly cancel itself out, and the net impact WILL BE big enough to sway some close elections from one column to another. Having an election go against the will of the majority of eligible citizens is a dire consequence. That's the high cost of imposing voter ID laws. So, what are the benefits? Are they enough to counter-balance the cost? Well, in theory, you'll be dissuading some number of ineligible people from registering a vote. However, all the evidence we have suggests that the numbers involved there are tiny. Very, very few people who aren't eligible to vote do so, for obvious reasons. In case the reasons aren't obvious to you, remember that those hypothetical voters, too, have their personal cost/benefit analysis. For them, the benefit is negligible: it's the infinitesimal possibility that their one ineligible vote will just happen to be the one that sways the whole election in the direction they want it to go. Meanwhile, the cost is significant: they're committing a crime and there's a chance of getting caught, resulting in serious repercussions. That's particularly true for illegal aliens. If a poll worker happens to know the person casting a vote and know he's ineligible and turns him in, we could be talking about deportation, for example -- something that would disrupt the person's entire life and cast him back, unemployed, into the third-world, while possibly breaking up his family. How many people, really, are going to want to risk that for the rather meager rewards of voting? Even for those of us with NO risk associated with voting, turnout rates are embarrassingly low, and lower still for the poor and minorities. So, the idea that a disproportionately poor and minority group of people who face such terrible risks if they vote will do so anyway, in any significant numbers, is just silly, fantasy-land conservative paranoia. This is simply not a significant problem in the real world.
So, there we have it. Imposing voting ID laws will almost certainly dissuade far more ELIGIBLE VOTERS than ineligible ones. It will almost certainly result in a much greater share of elections going the opposite way as the will of the citizens would have them go. As long as that remains the case, any American who cares about our deepest national ideals must oppose voter ID laws. If someone can make a reasonable case that voter ID laws won't have that anticipated impact, or if someone can propose a form of voter ID rule that gets around it, I remain quite open minded about it. But, for now, simple patriotism dictates my opposition. As a patriot, I must support the position that is reasonably calculated to make our elections more reflective of the will of the citizens. So must you.