As you well know, people use email for things they shouldn't. Why not make email slightly better? What's the harm? Isn't greatly reducing the chance of blackmail unequivocally positive?

So far, you've just been repeating disparaging comments on less technically minded ("stupid") people. You've not presented an argument for why this change would be detrimental.

We can continue educating people about the inherit insecurity of email while still improving it for those that (a) will never get it and (b) simply don't have access to alternatives.