I think part of it is fatigue. Having to explain the same basic principles over and over again creates the illusion that you're not accomplishing anything. It wears down on you and you and it can be sort of emotionally fatiguing. I know I've had days where I feel like I just can't explain another thing... and you know, we all came here to have fun.
That's right! Not one of us came here because we thought to ourselves, "man, my life could really use a lot of unpaid mental labor!" We all came to this forum to find something enjoyable; discussion, information, friends, whatever. We're understandably upset when our fun-time becomes a monotonous chore full of offensively stupid children disregarding our knowledge and efforts. That's actually a pretty sucky experience for something entirely on the internet.
Why not stop a moment and look at it from the point of view of the teacher? I've been studying magick for 14 years. That is to say, I've been a magician to one degree or another longer than some of these fluffies have even been alive. I spend a considerable amount of time on many of letters and posts not just writing them, but also researching my response so I can be absolutely sure and so I can refer my reader to a helpful source. And right now I'm actually sick, helping my boyfriend through a death in his family, looking and an impending death in my own, and supposedly getting ready to move across state in a few weeks even though I'm completely unprepared... and yet I'm here answering your question. I genuinely love magick and I believe that 14 years of magical study is something too important to hoard.
With that in mind, how do you think it feels to so frequently be told that our knowledge and efforts mean nothing because "I don't care, werewolves are real lol." Imagine if someone did the equivalent to a doctor doing volunteer work.
And that, Ronin, is how fluffies can make a man turn from helpfulness to the banhammer.