Actually, in the aftermath of 9/11, Bush opposed it, but the cowards in Congress forced it on him. He should have vetoed it, but didn't since he did not want to appear weak in light of the internal Al Qaeda threat, or give the Rats something else with which to beat him over the head with.
I remember that debate well, and it looks like the predictions made at the time that DHS would be ultimately be turned away from Al Qaeda and against U.S. citizens once Democrat administration took control of the government