Here is the way I see it. You have set a personal standard as to what caliber of fish YOU will keep (I do something similar with deer but that scale can slide depending on that year's conditions and how badly I want to eat sausage) and are upset when others don't share the same view. I understand that and it makes sense that if you harvest that dandy fish or buck, it isn't going to grow into a MONSTER. The thing is that alot of folks are quite tickled to catch/shoot a dandy, as they should be, and is it your/my right to rain on their parade just because they view is "skewed?"

I see several ways of dealing with it:
- rather then brow-beating them for keeping the dandy fish, educate them. Explain to them how releasing the dandies to grow into a MONSTER can benefit them, which you likely have, tell them how much better eating the smaller fish are, etc.
- don't fish with such folks and search out a group that share your view but know that this group will likely have other issues you will need to contend with.
- lastly, realize that what few bigger fish members of your party keep during the few days you are there likely have a negligible affect on the overall population of big fish. I understand that if everybody keeps these dandy fish it will be detrimental to the chance of any MONSTER fish but if your tripmates are the exception rather then the rule then I truly don't think it is a big deal.

Just my two cents worth.