It seems to me that humor and memes, when used in a hateful manner, have a toxic effect. They often blur the lines of morality and in effect normalize and seemingly validate dangerous thoughts and ideas. Words lead to thoughts, thoughts lead to behaviors, and what people read often have an impact on them whether they realize it or not.
Certain groups have been weaponizing this, and it's amazingly effective. A while back, people on reddit realized people on stormfront were organizing and coordinating to manipulate the voting to push their racist agenda. It mostly wasn't through overtly white-supremacist content though, it was primarily anti-PC offensive humor. Memes. BASICALLY the shit that litters tons of subreddits now. That was several years ago IIRC. You don't have to dig very deep into those comment sections before you find some beyond-questionable sentiments being thrown around.
There's a big push by white supremacists to normalize offensive humor of a certain breed: make something considered funny solely because it's really racist. In the Vice Charlottesville video one of the neo-nazis brags that their support is growing because people are "sharing their memes". I see this type of humor popping up a lot with my younger friends. It's not a clever punchline about a taboo subject, it's just really offensive. It works great as a recruiting tool because it A) steers people with latent prejudices into the arms of hate groups B) normalizes the ideas and rhetoric used by these hate groups so that impressionable people will be more receptive to it when the real pitch comes. It is definitely inviting people into a tribe.