to be honest i mainly do strength training for aesthetics...my power has been generally on the same level since i started boxing so yeah :thumbsup
Your power has remained the same because you haven't got any stronger since you're not doing strength training...
Explain to him the difference between strength training and his routine, and your rationale behind why you feel a strength routine may help his punching power. Maybe he just doesn't know the difference. :good
Weight training isn't skill training. You need heavy weight to recruit the largest fibres. You need heavy weight to improve the stiffness of tendons. You obviously shouldn't be lifting heavy weight just before a fight. Everything has its place in a periodised program. The OP is an idiot, you don't improve boxing performance while you are strength training, your performance improves when you stop.