"For verily, verily I say unto you, he that hath the spirit of contention is not of me, but is of the devil, who is the father of contention, and he stirreth up the hearts of men to contend with anger, one with another."
First things first, if you challenge a Mormon's religion, this verse makes him win a priori. The very fact that you're arguing with him proves the existence of the devil, which means Mormonism is true and you aren't. We both know, of course, that this is actually an example of begging the question, but there's no way he'd ever understand that.
Oh boy, where to even begin?
I hate the entire concept of "contention is of the devil" with (sorry in advance for the sickening cliche) every fiber of my being. I hate it. I loathe it. I completely detest it. But why do I hate it, loathe it, and detest it?
Because it's the rough equivalent of "talk to the hand, 'cause the face ain't listening" or "la la la la la! I can't hear you!!!"
Funny how hearing only one side of an issue is enough to prove its truthfulness, but hearing both sides is of the devil. Consider the following conversation (which, lamentably, is just a paraphrase of a real conversation):
Atheist: If I gave you a book that suggested a different view, would you read it?
Atheist: Doesn't that make you close-minded?
Mormon: You aren't willing to accept my position. Doesn't that make you close-minded?
Go, Mormon, go! Fight that evil Atheist! Satan has been beaten again! Long live the faith!
(Comically, the Atheist was actually an ex-Mormon. No, it wasn't me.)
Anyway, the biggest problem with the "contention is of the devil" mindset can be explained with a little analogy:
Imagine that there was an armchair in your living room that had a large rusty nail poking out of one of the arms, so that whenever you sat in it the nail would cut through your thigh and blood would get everywhere. Wincing in pain, you still sit in the chair anyway, because that's just what you always do. When you're done sitting there, you get up, wipe off the blood, put on a bright and happy Band-Aid, and go about your day.
You can't remove the nail because doing so is "of the devil", and you can't just sell the chair and get a new one because it's the chair your great-great-grandfather used when he was your age... and you'd be disrespecting him if you sat in a different chair.
The thing is, the whole "contention is of the devil" thing fixes problems like Band-Aids fix your thigh; sure, it looks like you're making everything better, but chances are you won't be able to walk on that leg a few years down the road. You might not even have that leg anymore.
... and that leg doesn't want to fall off, though it might have to.
Another interesting byproduct of this pseudo-axiom is that, put bluntly, your average Mormon sucks at arguing. He sucks at putting his argument into words, he sucks at hearing your argument, and he always assumes your argument is said with a very hostile and violent tone. Take this, for example:
I quite strongly disagree with you, sir. Disallowing gays to marry is not going to make gays go away. It won't make gays turn straight and it definitely won't stop them from making out with their boyfriends in public. You're trying to ban homosexuality, not gay marriage. Quit confusing the two.
Not really hostile at all, right? Just firmly presenting a different opinion. Your average Mormon, however, being totally unaccustomed to different opinions, and assuming contention is inherently hostile, would read that paragraph like this:
I hate you and I hope you die, you worthless piece of excrement!!!1 Gays aren't gonna go away, whether Prop 8 passes or not, so you can go cry to mommy like the little girl you are. Your views are insignificant, and I laugh at your futile attempts to even create a sentence. What are you, 8 years old?
(Wow... I enjoyed writing that a little more than I should have.)
So, let's summarize the dangers of contention-hating into a few bullet points, shall we?
- It is a barrier to finding Truth.
- It treats the symptom, but not the cause.
- It makes you a n00b at arguing, and arguing is an important skill you use every day.
- It freaking annoys me.
That last point is the most important one, by the way.