Ask yourself this: would you like to have your rare/unreleased stuff leaked? I'm sure you wouldn't. So we have to respect the wishes of people who post. If the rules say "don't spread/share/trade/sell this stuff", then you have a choice: either play by the rules or leave. If you can't play by the rules, you're dishonest to say the least.
I've been lucky to receive some acapellas and stems by local bands here and even though I think more remixes would actually benefit them, I simply don't share them just because I was asked not to.