Is Iran Really Arming Insurgents?

Why all the outrage over Iran selling arms to one side in the midst of a war? It's damn good business...and nothing different to any other nation's arms industry selling their wares on the open market.

Perhaps it's because the US military doesn't like the fact that the enemy they are engaging won't fight by their rule-book, or only limit themselves to fighting back with rusty AK's and RPG's.