Do you think Shakespeare's main message in Othello is "Don't trust outward appearances"?

I tend to agree with this statement, as the tragedy in Shakespeare's Othello relies upon deceptive appearances and exploited assumptions about these appearances. After all, Iago is able to dupe Othello (and pretty much everyone else) so effectively because he successfully makes himself seem like a loyal and trusted advisor. Similarly, Iago is able to manipulate and warp the appearances of other characters, most notably Cassio and Desdemona, in order to make them seem like scheming traitors. As such, the play's tragic ending is a result of mistakenly assuming that one's appearance is an accurate translation of one's character. Since Iago is the mastermind behind these deceptive appearances, his quote in Act III, Scene 3 is especially ironic: 

Men should be what they seem;

Or those that be not, would they might seem none (130-31).

In this passage, Iago is essentially saying people should be what they appear to be. In light of the hidden, villainous nature of Iago's character, this assertion becomes one of the play's most disturbing (and fascinating) quotations.