If Loughner had been unable to get a gun, he would have found another way alright. This was the parking lot of a grocery store. He could have caused just as much mayhem by plowing through the crowd with his car. But none of these geniuses would be blaming the car.
According to his friends, he often went target shooting in the desert with them.
So, he obviously already had access to guns.
Loughner committed mass murder. He would not give a hoot about a minor thing such as a gun law. So , instead of blaming the person, you blame the inanimate object he used.
I agree with you, Loughner would have used anything he could have gotten his hands on. It would have been a pipe bomb and that would have been much worse.