Darcy should blame himself IMO. He rationalizes his arrogant treatment of Jane and Bingley into something to be proud of. I intend to focus on his judgment of Jane although I feel his treatment of Bingley bears scrutiny also I will leave it to another post. Darcy’s judgment and the logic of it is flawed IMO and I am by no means convinced that he was not swayed by his own desires in the disposal of his friend in marriage. I think his interference with Bingley’s intentions towards Jane is very little gentled by his explanations; he gives a believable, logical scenario which does away with any personal wish to hurt Jane but it highlights his intolerance and uncaring attitude for people he considers inferior.

Your sister I also watched. Her look and manners were open, cheerful, and engaging as ever, but without any symptom of peculiar regard, and I remained convinced from the evening's scrutiny, that though she received his attentions with pleasure, she did not invite them by any participation of sentiment. (Chapter 35)

It seems to me Darcy actually had the very best indications that Jane was anything but indifferent to Bingley. First, “she received his attentions with pleasure” and second “He (Bingley) had before believed her to return his affection with sincere, if not with equal regard.” I do not know what “symptom of peculiar regard” or “sentiment” Darcy expects for Jane to do or say in a ball among many people and before Bingley has declared himself to her. Darcy is putting a burden on Jane which IMO is not hers to carry. Darcy, like Charlotte before him (Chapter 6) does not consider Jane’s reserved nature, “But she does help him on, as much as her nature will allow. If I can perceive her regard for him, he must be a simpleton, indeed, not to discover it too." Bingley is not a simpleton and was aware that Jane returned his regard; she showed the only person who mattered that she did like him.

If you have not been mistaken here, I must have been in an error. Your superior knowledge of your sister must make the latter probable. -- If it be so, if I have been misled by such error to inflict pain on her, your resentment has not been unreasonable. But I shall not scruple to assert that the serenity of your sister's countenance and air was such as might have given the most acute observer a conviction that, however amiable her temper, her heart was not likely to be easily touched. (Chapter 35)

Although Darcy admits he was likely wrong about Jane’s feelings he still does not admit to doing her a wrong nor does he apologize to Lizzy for the pain Jane has suffered. Charlotte decided she understood Mr. Collins well enough to marry him within four days (;D) but Darcy has her beat because he can determine, just by observation, the availability of a lady’s heart in just one evening during a ball where her attention naturally must be divided. Darcy does not even suggest that he spoke to Jane during the evening; do we know if he ever actually had a conversation with Jane other than “a polite congratulation” in Chapter 11? IMO Darcy’s readiness to assure Bingley of Jane’s indifference on what amounts to no evidence is really overbearing and unfeeling. Is part of his motivation to ensure Lizzy will not be around to tempt him as she would if Jane and Bingley continued and he returned to Netherfield?

The situation of your mother's family, though objectionable, was nothing in comparison of that total want of propriety so frequently, so almost uniformly betrayed by herself, by your three younger sisters, and occasionally even by your father. Pardon me. It pains me to offend you. But amidst your concern for the defects of your nearest relations, and your displeasure at this representation of them, let it give you consolation to consider that, to have conducted yourselves so as to avoid any share of the like censure, is praise no less generally bestowed on you and your eldest sister, than it is honourable to the sense and disposition of both. (Chapter 34)

Darcy ultimately justifies his interference because of the impropriety of some of Jane's near relatives. When he writes his letter he knows Jane did have affection for Bingley, she behaves always with propriety by his estimation yet he chooses to uphold his interference solely because she has three silly sisters, a foolish mother and a satirical father. I think he is grasping at straws, especially when I consider that he was willing to overlook the sisters, the mother, and the father so long as Lizzy would marry him and in addition he has his own embarrassing relative to bear. Lady Catherine acts inappropriately and Darcy was “a little ashamed of his aunt's ill-breeding” in Chapter 31. Yet, Darcy still holds Jane’s family against her and I think it is a bit two-faced—I do not suppose he believes himself less worthy husband material because he has an arrogant, vulgarly inquisitive, demanding aunt.

"I do not see what right Mr. Darcy had to decide on the propriety of his friend's inclination, or why, upon his own judgment alone, he was to determine and direct in what manner that friend was to be happy.

"That is not an unnatural surmise," said Fitzwilliam, "but it is lessening the honour of my cousin's triumph very sadly." (Chapter 33)

Col Fitzwilliam was right about affection between the couple lessening the honor of Darcy’s triumph and Darcy should have been sensible of it but he is not. Darcy is not ready to admit he was wrong. Although I do not like his interference, I can accept the argument against the evils of the connection as logical for a gentleman so far above his company in general but I do not care how serene Jane’s countenance was, Darcy steps over the line by convincing Bingley Jane does not care for him. One last thought, does Darcy’s judgment of Jane’s serenity as indifference shed any light on why he has consistently misconstrued Lizzy’s playful manners as encouragement? Jane’s reserve is interpreted as indifference to Bingley while Lizzy’s playful manner was interpreted as some sort of esteem towards him. Darcy is wrong on both counts and it sounds all too familiar. Lizzy often misinterpreted Darcy’s reserved manner as dislike and Wickham’s happy manners as real esteem for her but he easily abandoned her for Miss King and her ten thousand pounds. I think after the blow up at the proposal and the receipt of Darcy’s letter they are finally seeing each other without a lot of misconceptions—any thoughts? ;D