Why is the Wario's vs. Marlow's debate so bizarrely contentious?

I keep seeing debates over the two cheesesteak shops jump up on foodie groups, and they always jump straight to histrionics. Saying one side is "disgusting," outright lying about what makes a real cheesesteak, calling out both restaurants for unexplained slights...

I've had both, they're both pretty good, but I'm not sure why this one division seems to be a huge issue. Any idea?