What's the verdict on this? Legal? Illegal? IMO you have to protect yourself at all times. This was in the 7th round, can't drop your gloves there. The chivalry of the fist bump is all there is to that. The other guy was perfectly in the right to try to KO him. I mean, this is very reminiscent of Mayweather's KO of Victor Ortiz.
I mean, the ref says before the fight, "Protect yourself at all times," so this kind of stuff is totally legal. It's pretty stupid to keep 0 guards up when fighting, but this is when unwritten rules of engagement can bite you in the ass. The Ref allows you to touch gloves at the beginning of the fight; once the bell rings it's fight on. Maybe not the most kosher, but as a boxing champion myself (1-0), I must stay true to the sweet science.