I just finished the golden claw quest then headed north towards Whiterun where I run into 4 imperials escorting a prisoner, I opt to free him and killed all the imperial guards. Upon returning to Riverwood to sell their loot the whole town turns on me and tries to kill me! I thought Imperials were their enemies why are they mad at me? Oh, I'm not sure if this affects my alignment but earlier when Gurder gave me the key to her house I took everything and sold it off for gold and I figured it was ok since there was no "steal" indicator and nobody reacted to me taking everything. Anyway why is Riverwood attacking me!?

Not everybody are Stormcloaks O.O

The blacksmith of riverwood openly wants the imperials to win.

Riverwood happens to be just fine with the Empire.

Stormcloaks are the enemy of the people at Riverwood and Whiterun, I'm sure that's why you are being attacked, you freed their enemy and killed their allies

Alot of those small towns are split also. Some of them like imps and some like cloaks.

I'm freed prisoners of both sides while killing their escorts, river wood's townspeople have never attacked me. Maybe you accidentally stepped on one of their chickens and now their mad?