Pretty much what Azu said. I like reading the different opinions of others, be it anime related or on a more serious topic. And "this is an anime forum" always sounded like a silly statement made by someone who don't see the bigger picture, at least in the context that it seems to be used. If I frequently eat inside a McDonalds, and happen to get in some deep conversations with some of the other patrons, and actually learn a few things, will I say "McDonalds taught me so much!". No, it was the people inside McDonalds. This same logic can be applied to online forums, and yes, even an anime forum. And since forums revolve around discussion (unlike McDonalds), it should be expected. If you limit your opportunity for knowledge and wisdom to a time and place, then you're limiting your knowledge and wisdom. People who are from different cultures, specialize in specific fields, possess more general knowledge than the average person, have unusual experiences to share, or simply have a unique perspective visits forums frequently.
"That's why you have books and Google..."
Books and Google is limited, in that it can only teach you about the topic you're researching, and sure, sometimes the topic can be a bit broad. The topic you choose to research can only be researched if you have the thought to research it. On a forum, all kinds of different topics are thrown at you, you don't have to be thinking about it. And if you're one to gain all your knowledge from books and Google search results, then cool, maybe you can be one of those sharing it on forums when you feel you're ready.
That said, the decision to not discuss anything serious on a forum/anime forum isn't completely unjustified.
> Flaming
> Trolls
> Members who refuse to accept anything, even if fact
> Insults over an opinion, or an opinion given that is lacking in knowledge
These four can make discussion not very fun, especially the last one. We're all ignorant to an extent, and this can envelope one in fear or an uneasiness to speak out on a topic. Flaming can produce the same effect. And the other two can just make discussion meaningless. I also noticed that when a member talks about a view or belief in one thread, they may become the target of aggression for that same opinion/belief in another thread. So add judgmental to the list.
This doesn't happen in every thread though, and people can and do get into some great discussions. If "this is an anime forum" is used in a way that implies it's derogatory to learn anything on an anime forum, then that person either has their nose high in the air, jumping on a bandwagon (without any idea on why they're actually doing it), or only see the negatives that is inherent in an anime forum.
So yep, I like reading the different opinions and beliefs. We don't have that luxury in real life, if you just go up to random people, you're more likely to annoy them, or not obtain any noteworthy info, since it can sometimes take time to formulate out thoughts on a topic (another benefit of forums). Not to mention it can make people uncomfortable, and more likely to agree with you, than offering some opposing views.
People don't keep their opinions and beliefs tattooed all over their body in real life, and if they did, they can probably keep their opinions to themselves. It can be hard to focus on the opinion at hand, if you have to stare at their ass, or they're being a ****. Though, I guess that last sentence applies to forums as well.
Yep, that's about it. Differing views attracts me. Making friends is nice as well. Also what Kibouu said.