Senate Debates Immigration: Why?

Today, debate began in the Senate over a Bush proposal to allow amnesty for 11 million illegal aliens in the US right now. And I find myself wondering why? What's the point?
If the Congress passes a bill that Bush doesn't like, one of two things will happen, as Bush has done in the past. If they pass one similar to the one Bush would like to see passed, he'll just sign the bill he would like to see passed in place of that one. He has done that before, a few weeks ago, he signed an appropriations bill that was $2 billion different than the one passed by Congress. If the Congress passes one that goes against the wishes of the Bush administration, one that a majority of Americans would like to see passed, such as the McCain-Feingold bill on torture, he'll just issue a signing statement that says he doesn't have to enforce the law. Congress has become like the UN in the Bush's eyes, irrelevant unless it does exactly what Bush wants. The checks and balances envisioned by our founding fathers have given way to those who believe in a unitary executive (i.e., a dictator), as long as that unitarian executive is their guy.
So while the Republicans jockey for position in the Senate over where to take this legislation, the battle lines drawn have already shown who will win. Bill Frist, looking at a 2008 Presidential run, has appealed to the racist anti-immigration majority in the Republican party. Sam Brownback, while in favor of strengthening our borders, would like to grant amnesty to illegals already here, in a move to appeal to the business end of the Republican party who would like to increase profits by flooding the labor pool with low wage employees rather than take a pay cut themselves. Who will win? It doesn't really matter who wins, because no matter which bill passes, America will lose because of the actions of the Bush administration, who, like every other member of Congress, is in the pockets of big business and will do what's best for them to the detriment of the rest of the country. Remember NAFTA? Remember CAFTA? These bills were passed against the objections of a majority of Americans so big business could send jobs across our borders. We were supposed to see the price of things go down, but unfortunately, because of the high price of fuel to move products, as well the increased trade deficit created by this move, the prices of most things haven't gone down, the only increase has been in the salaries of CEOs across the country.
So why debate this? Why not just roll over and expose your soft white underbelly? It doesn't matter what Congress does, so why in the Hell do we pay the bastards? As Justice Sandra Day O'Connor said a few weeks ago, America has begun a slide into a dictatorship (thanks in part to you, you bitch), and since nobody in Congress appears willing to stop it (okay, Russ Feingold, but who else?) why don't you just vote to dissolve yourself and take a job on the board of directors of some corporation, because you're obviously not working for the people anymore.