A lack of emotion makes you guilty?

I was reading about Amanda Knox and most people in the comments of the article are in favor of having her lynched.

Why? Because of the speck of DNA on the kitchen knife that wasn’t even consistent with the stab wounds on Meredith Kercher and the fact that she hasn’t been seen “actually” crying on public television.

Apparently the lack of emotion makes her “guilty, guilty, guilty” and a “filthy liar”.

It made me think of myself…I never have been one for big shows of emotion. It’s not a conscious effort to suppress emotion, I just don’t.

I was also thinking of our own court system. The people leaving these comments are the same people on juries. They’re willing to call a woman a murderer even though there’s no substantial evidence…they’re just going on their own opinion and “feeling”.
I think it was Mark Twain that said people do a lot of feeling and mistake it for thinking.

So, how does not having an emotional fit make someone guilty?