This article isn't about me. I'm not the most bullish MannKind (NASDAQ:MNKD) investor ever.

But I have to start with a confession about myself: I'm a bit of a hypocrite.

I think CEOs should have skin in the game; owning a portion of their company helps align the CEO with the rest of its shareholders. And yet, the bullish nature of Alfred Mann, who has beneficial interest in around half of his namesake biotech, scares the crap out of me.

Check out what Mann told PharmExec about the potential approval of MannKind's inhaled insulin Afrezza, "I would expect it to be approved in mid-April [2014]. On our schedule it looks like April 14, but it could be a few days before or after."

Calling out the day of the approval -- before you've even submitted the data to the Food and Drug Administration -- it doesn't get much more bullish than that.

Before you hit the buy button though, consider this quote: "MannKind Corp. expects the U.S. Food and Drug Administration to approve its experimental inhaled insulin device 'within days' of inspecting a manufacturing plant that supplies the insulin, the company's chief executive said on Tuesday."

That ones from a Reuters article in 2010, a few months before the FDA rejected Afrezza. During that interview, Mann even made a comment about talking with the FDA about the drug's label. That's a not-so-secret code between CEOs and investors that the FDA is in the final stages of approval; there's no reason for the agency to be worried about the label if it's not going to approve the drug anyway.

As the saying goes: Fool me once, shame on you; fool me twice, shame on me. Even if Mann uses the secret knock, I'd advise against letting him in the clubhouse.

Of course, I'm already a card carrying member of the "Afrezza will be approved" club, but Mann saying that it'll be approved doesn't give me any more confidence.

In fact, given his track record, it's hard to take any of the bullish things he says seriously. My main concern with Afrezza's potential is that doctors won't be willing to switch patients from injectable insulin -- Eli Lilly's (NYSE:LLY) Humalog and Novo Nordisk's (NYSE:NVO) Novolog -- to inhaled Afrezza because of worries about potentially unknown side effects. The caution will create a really slow launch until doctors become comfortable with the new mode of delivery.

Mann blows off the idea, citing that Afrezza is a better product. For his sake, I hope he's right.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.