I've found a great way to go about criticising someone without being so direct. Imagine this:

A: "Sigh. He's so smart, unlike us. Stupid and blur."
B: "?!" (Like what has that got to with me?)

Hah - actually the hidden meaning is that A have always wanted to say that B is dumb, but just not the usual way. Like this, B will never suspect A's word game since even A is willing to call him/herself stupid and blur.

Don't be fooled, alright? The impact of one scolding oneself is as strong as a feather crashing to the floor.