You have touched on JA's ability to delve into maleness. We often see her use male characters for heroic or comic effect, but here we see a wonderful example of her ability to realistically and accurately display a common and typical male characteristic: James is smitten by the first glamorous woman to have paid attention to him. One wonders how much of JA's observations of her own brothers informed her talents on this matter.

As you put it, "He cannot see how his affection for [Isabella] has compromised his judgment and values and caused him to do wrong by his sister." Isabella is a new experience for James, and he responds in a way so typical for a lot of men; just ask any guy how he behaved when the first truly gorgeous/glamorous woman that they thought were completely out of their league showed a sign of returning the guy's interest. It can be humorous to watch at first (those puppy dog-style behaviors), but unless it works out for a longterm relationship the end can be a train wreck for the poor slouch. It will be interesting to see how this all turns out for James.