The first mistake was putting two untouched dogs on each other. This is a great way to teach bad habits and really slow down schooling. Also most times than not you won't get what you want out of it. Not saying this is true in all cases as there are untouched or young dogs that know what todo instinctively but if you're going todo it you might as well do it the most logical way. You want to use a dog that you know will go over there and take hold when you need it to and give the inexperienced dog some good looks.

Personally I wouldn't keep those dogs as I have no need for 3 year old dogs that won't go but if your partner thought he saw something in that dog or feels like it just needs some more time to figure out the deal then more power to him. If you respect him enough to call him a partner then give him the benefit of the doubt. Very rarely will two people agree on everything all the time. Now if he starts making a habit of keeping curs or making excuses for dogs and that's not what you're about then you might want to think about parting ways.