I'm sure there are many valid reasons to buy this.
Because semi-automatics don't do enough damage, really. And how else are the people at the rally going to know that I hate Obama while I'm brandishing my gun?
I feel like this would be a perfect time for normal, reasonable conservatives to step in and say, "Hey, you ultra-right-wing nutbags are making us all look bad. Wanna cool it with that shiitake?" That's what I would do.