How does calling someone an "idiot" make one subject for gehenna? I'm sure there is something of translation, meaning, or ancient culture to be considered here.

[Matthew 5:22][1]

> ...and whoever says, You [d]cursed fool! [You empty-headed **idiot**!] shall
> be [e]liable to and unable to escape the hell (Gehenna) of fire.

 - Is this a point lost in translation? 
 - What is the point Jesus is
   making when he said this?