possibly brought about by your colleague saying "STOP!" instead of "Rotate"
This policy by some operators of empowering the first officer to use the word "STOP" frightens the hell out of me. Will that cause the captain to blindly abort the take off (or rotation worse still) without knowing exactly what perceived event caused the PNF to make this loud squawk. Thread creep I know but surely the safest action under these circumstances is to call the nature of the problem eg engine failure or fire, master caution door open and so on and it is then the decision of the captain to take the required action