Just teach him that this is not just material worth some money, but that you put your time and effort into, and you want to share it with someone who values it the same than you do, and have a great time enjoying it, good relaxing conversations, - or whatever it is, i dont know you - and theres a lot of good dope out there, that he can find others..... maybe he gets the point. with that you still show him the rspect that you not dislike him just because he is unreasonable.
I think you mean disvaluing the results, beeing ungrateful, as if it was easy, cheap, "nothing". Sure it's not.
I mean if you show him molded buds and say, oh all got rotten, you cant smoke that, i dont even have enough for me...some day in the future it going to be the same. How long do you want to continue that ?