1-3-1 is a form of the Neutral Zone Trap. It's basically a balls out, totally committed, we don't give a shit about offense it's all defense strategy.

This is a good X's and O's explainer.

http://buffalosabresnation.com/2011/11/21/the-1-3-1-neutral-zone-trap-explained/

It's just controversial because when it's done well it significantly limits any offensive chances and makes the game boring as all hell from a viewing standpoint.