There are lots of angles to this, and we've heard most of them. The most common is probably noting how much port security, enhanced information systems, etc., could have been bought for the hundreds of billions that we've poured into disproving the neocons' fuckwitted theories in Iraq.
Another angle had me particularly seething, as a New Yorker, in the run-up to the Necropublican Convention celebrating the anniversary of 9/11 last year. As you probably know, "homeland security" money is being wasted on red-state locales that don't need it, while places that have been hit and are the most likely future targets (New York and Washington, for instance) are getting screwed.
Josh Marshall has been running some interesting posts lately about how corruption has become a near-GOP monopoly in Washington because of things like De Lay's K Street project and the increased use of earmarking in appropriations bills. In ways both corrupt and legitimate, the GOP machine has perfected the art of bringing pork to Republican districts. This is bad enough when it sends hundred of millions to Alaska to build a bridge to nowhere, but it's even worse when it takes security funding away from places that are most vulnerable.