How does darcy justificate his reasons when elizabeth accuses him?

Aside from arrogance, conceit, and carelessness of the feelings of others, Elizabeth accuses Darcy of two things, preventing Wickham from getting a preferment due him as an inheritance from Darcy's father, and separating Jane from Bingley.

Simply put, Darcy says that Wickham asked for, and received, cash instead of the preferment, and then won Darcy's animosity by trying to elope with Darcy's fifteen year old sister to get her inheritance.

Darcy's claim on the issue of Jane and Bingley is that he observed Jane closely and came to the conclusion that she was not in love with Bingley, so he advised Bingley to stay away from her instead of letting himself fall in love with a woman who would not return his affection. Additionally, he perceived a desire on the part of Jane's mother to have her marry Bingley for money, which was compounded by a lack of refinement on the part of both Jane's mother and other members of the family and a general lack of good connections.