Some of us object to conspiracy-mongering because we know people are only human, and have a limited capacity for outrage and action - there's only so much we can do beyond taking care of our families. At the same time, we know that plenty of objectionable things that deserve our attention are happening every day - things that are known and acknowledged to be happening, things that may be perfectly legal and constitutional but are nonetheless repugnant.
When the public's attention is drawn to an entertaining and sexy conspiracy theory, something that might have happened but very very probably didn't, the public's attention is no longer focused on the absolutely-100%-objectionable things taking place every day. That's why conspiracy-mongering is a net loss for society, and why I'll happily crack tinfoil hat jokes at the author's expense - it's not because I think the government's a big group of lovable folks, it's because all that time we're collectively spending writing the script for a future episode of Ancient Aliens could be so much better spent.