All 3 are to blame.
Ortiz shouldn't have dropped that 'headshot' intentional or not.
Cortez is a retard for not paying attention, after they touched gloves he should of seperated them, but no, he looks away at who knows what the fuck.
Mayweather didn't do anything particularly illegal, after you touch gloves you can hit, but he took advantage of the situation and took a cheap shot, very classless.
In the end, unprofessionalism of all 3 turned this into a hoopla of trash, but I place Cortez as being the biggest fuck up as he's supposed to be the authority figure in the ring.