I quite agree to say that Bob protects his Dairy Cows because this is quite true and there have been several times he has done this.
It doesn't matter what I think Inoue should be one of his opponents because it's really not funny if it doesn't happen especially if he does win against Butller
For Bob, boxing is business, so he will make sure that his investment will give him a profit, and he will not put his fighter at risk of losing because it will lose the value of his boxer and he won't be making a lot of money from a boxer. Just for example, if Inoue fight Casimero and Inoue lost the fight, that is a big lose for Arum as Inoue being a pound for pound fighter will lose his belts and will not be a champion.
Indeed, he surely knows what to do to make money in this industry with minimal risk involved and won't likely pursue any fights that won't be any good for him especially if it's Inoue or one of his best cash cows, but for now Bob is ain't interested about Casimero yet. So, Casimero should really secure this fight against Butler if he really wants Inoue to fight him. In that way, he has more chance rather than just talking trash to provoke the other side.
I think he is being too careful but indeed this might be a pretty good move for him because indeed Casimero is not an opponent that Inoue can really fight even though Inoue is quite strong but Casimero is above him and indeed Bob certainly predicts this
It is kind of natural for the promoters to make sure that their best boxers aren't in the disadvantage side especially when the money deal is not that reasonable for them. Not just Bob Arum but others as well do this kind of things because business is business. For now, Casimero is the one who needs Inoue to him to of course benefit and be more known in the industry but as I said, Bob ain't interested and surely had other plans for Inoue.
In that same note, Casimero should make this fight against Butler in his favor if he is that passionate to make Inoue as a stepping stone for his career because if indeed Casimero will upset Butler then Bob Arum can't avoid anymore and make Inoue fight Casimero.
In side of Arum maybe he thinks that he cannot get anything huge if they let Inoue fight with Casimero and their fighter will be at huge risk if Casimero surprisingly defeat him and this one can lower the stack of their current favorite fighter. This is the reason why Casimero need to have impressive win against Butler so that Arum cannot resist to make this fight to happen since the fans calling about it will surely be much stronger.