A large part of the increased aggression online is because of anonymity. The ability to speak about things that may hurt others with no consequences is a powerful motivator. With no obvious or concrete path to real world lash back the confidence to say or do whatever regardless of social standards or the thoughts of others.
There is a large difference between cheating and peeking at strategy guides. In single player games, cheating and such has no larger consequence, the only person it effects is the player who chooses to do so. In this way it could be considered the same as an artificial or self-imposed rule to increase difficulty. If the player wishes to have an easier gameplay experience and cheating is the easiest way to do so there is no reason why they shouldn’t be able to. In games where others are effected by cheating, the feeling of power when absolutely overpowering someone or showing off expensive or rare items. "cheating [is] more likely in what they [researchers] called 'performance-avoidance' situations where you were trying to avoid doing worse than someone else." (Pg. 28).Unfortunately this often also destroys the experience others are looking forward to. Which is why this is even an issue, if cheating is isolated and inconsequential there is no need to discuss it.
Fans being willing to fight is an obvious one, belonging to a group or connecting with a story / character / environment in a powerful way makes people exceptionally passionate. When someone insults or attacks something a person feels exceptionally passionate about they feel obligated to defend it. Imagine knowing a specific scientific theory. If one sees it being misused or misrepresented online, you would feel obligated to correct them or at least inform anyone who found the comment later the truth of the matter. Now understand that usually these people know for a fact that the product they enjoy is an amazing experience and even with flaws is powerful and enjoyable. If someone says online that it is bad, a fan would feel obligated to correct this. And many times if someone feels strongly enough to do so it would not be the first time, giving the same argument and seeing the same insults over and over again would lead to a lot of aggravation and hostility towards the people they are attempting to correct.