This poster works great at reinforcing the types of sentiments that we here all share. In other words, it is great at "preaching to the choir".
I fear that it can do little else.
The message that you are sending is an assertion that potential mass-murderers would rather attack a disarmed locale than an armed locale. This is not a particularly strong message in support of our cause. Its weakness lies in the fact that it is a non-issue in the campus carry debate.
The issue that comes up over and over and over again when debating campus carry is the responsibility level of your average college student. When you start talking about arming students, people think that you want to pass out guns at the campus entrance. Sadly, some of we pro-gunners, in our zeal to provide counter-examples, state that we would do just that ". . . if it were up to me."
The vast majority of people who are anti-campus carry are so because they believe that normal students allowed guns would be more dangerous that a VT massacre every few years. If you could wave a magic wand and totally convince 100% of the population that arming students would prevent all mass-killings, you would not have made any progress in the debate.
People see college as a large mixing bowl where you "mix" certain "ingredients" like alcohol, drugs, stress, "emotions" and if you are going to "throw guns into the mix" it is a "recipe for disaster", like the corner of your giant spatula is going to get caught on a trigger.
If you want to have an effect on the campus carry debate, you need to start framing the debate in the proper ways. This includes addressing the responsibility angle, make it clear that we don't want to arm students, we want to prevent students who are normally armed from being disarmed. Provide counterexamples like the state of Utah, and that campus in Virginia that allows guns.
As soon as you find yourself saying "if one goes berserk, another will take him down", you have lost.