I admit that I honestly do consider many people insane; and I always did.

I don't think you do, I think you consider most people to be (in some sense rightly) wrong or ignorant. Just the fact that you hold people to some standard (which you must do, if you say that they fail) means you don't think of them as insane. If you've ever known someone with depression or who is bi-polar disorder, you know that you can't tell them t snap out of it, or learn this or that, or just think it through. Even calling people insane, as an expression of contempt, is a way of holding them to a standard. But we don't hold actually insane people to standards, and we don't (unless we're jerks) hold them in contempt. You don't communicate the inconvenient truth to the insane. You don't disagree or agree with the insane. The wrong, the ignorant, the evil, yes. But not the insane.

No one here (and I mean no one) actually thinks the world is full of insane people. That's a bit of metaphor and hyperbole. If anyone seriously thought that, their behavior would be so radically strange (think 'I am Legend' or something), you'd probably find them locked up somewhere.

Is there a way to disagree with the majority, be open to new members, and not seem dangerous?

The claim that everyone else is insane doesn't sound dangerous, it sounds resentful. Dangerous is not a problem. I don't think we need to implement any of your ideas, because the issue is purely one of rhetoric. None of the ideas themselves are a problem, because there's no problem with saying everyone else is wrong so long as you have either 1) results, or 2) good, persuasive, arguments. And if all you've got is (2), tone matters, because you can only persuade people who listen to you. There's no reason at all to hide anything, or lie, or pretend or anything like that.