See...I kind of agree with you on the first point, but kind of not tpdancer. Any discussion, especially with differences of opinion, represents an investment of time and emotional energy. Some appear to be worth it (and often they are, ending with both parties having a better understanding of the other), and a great many, especially about gay topics, simply aren't. Not often, but on occasion I've chosen to stay quiet here because I came to the conclusion that a given discussion simply wasn't worth my time (which it's going to take a certain amount of) or my energy (which I can have a little more control over sometimes, hopefully, if I don't let some things get me all worked up).
That first reason ties into your second reason then. YES, we've all rehashed the basic arguments. Truth is, though, if we think someone's here in good faith (specifically new folks), and they've done the effort of a basic forum search before trotting out the same question, it goes a ways towards implying that that discussion might be "worth it". Even if it's strikingly similar to ones we've had last year. Even if it's boring and passe for us, it might be worth it (though it's a lot more worth it to find the dead thread, link it, and pick up from there).