If the guy decked him immediately after FofFX tried to kick him, it's no longer a cheap shot. It's self defense. If a guy attacks me while his back is turned I'm certainly not going wait for him to turn around before I defend myself. Big guy is innocent of a cheap shot imo.

Regarding FofFX's accountability for his actions, though, is up in the air. His behavior sounds to me like what someone that is mildly autistic might do. (I'm not an expert on autism by any means, but I've interacted with several autistic people and there are striking similarities.) There are also people that are just entirely clueless regarding social norms and expectations. I've never met a person like this that was married, but I suppose it's possible. But can you really fault someone for poor behavior if they are completely oblivious to it? I'm not sure you can.