Here's how my group have decided to rule the Backlash card:
Bob: Plays Poke in the Eye on Carl
Carl: Can defend but Plays Backlash.
Bob: Takes the 1 point of damage but since Backlash just reveses damage done and not effects Bob can still play his basic attack on Carl since Carl is considered "Defenseless."
This goes for Uppercut² as well. Bob would take the 6 points of damage but can still use his basic attack on Carl. This comes from a previous clarification we got on the forums. [url]Lunch Money Questions (Backlash and Humiliation)]
Note: You can not Backlash a Humiliation.