If this graph isn't just made up bs in the first place, one thought I recall from every major college campus I've been to is random religious preachers camped out every day telling everyone they're evil, subhuman, and going to hell. Guessing the atheists find that a little more annoying and worthy of shouting back at than some of the religiously inclined.
Nazi: "white power!"
Normal people: "hey, stfu!"
Cristian Conservatives: "hey I don't agree with it but let's hear him out. Some people might agree, his ideas deserve to be discussed and given a platform"