I agree 100% that Darcy's behaviour in the proposal cannot be excused. I am merely saying that Darcy's behaviour in the proposal does not mean that he doesn't care for Elizabeth's feelings at all. There can be different explanations for bad behaviour.

I personally think Darcy thought he was courting Elizabeth. Courtship in Regency England appears to have been obliged to be rather subtle. It's notable that JA never reports Darcy as explicitly saying something like "Will you marry me?" in his first proposal but Elizabeth just recognises his declaration of love as a marriage proposal - the assumption is that a declaration of love can only be a marriage proposal. Therefore finding out about the other person's feelings before you declared yourself was a process even more fraught with danger than modern day courtship.

There is no mention of balls during Elizabeth's visit to Kent, so Darcy couldn't have asked her to dance twice, which seems to have been a significant way of indicating interest. Darcy did call on Elizabeth and he did walk with her in the park several times.

He also appears to have talked to Elizabeth in ways that may mean a sounding out of marriage:
"It is a proof of your own attachment to Hertfordshire. anything beyond the very neighbourhood of Longbourn, I suppose, would appear far."

As he spoke there was a sort of smile which Elizabeth fancied she understood; he must be supposing her to be thinking of Jane and Netherfield, and she blushed as she answered --

"I do not mean to say that a woman may not be settled too near her family. The far and the near must be relative, and depend on many varying circumstances. Where there is fortune to make the expence of travelling unimportant, distance becomes no evil. (chpt 32).
Now Elizabeth interprets this as Darcy thinking of Jane and Netherfield, but it is possible that Darcy is instead thinking of Elizabeth and Pemberley (which is rather far from Longbourn).

And consider later on in chapter 32 when Elizabeth keeps running into Darcy in Rosings park:
More than once did Elizabeth, in her ramble within the Park, unexpectedly meet Mr. Darcy. She felt all the perverseness of the mischance that should bring him where no one else was brought, and, to prevent its ever happening again, took care to inform him at first that it was a favourite haunt of hers.

Darcy could interpret the information that this is a favourite haunt of hers as Elizabeth encouraging him to find her there.

How it could occur a second time, therefore, was very odd! Yet it did, and even a third. It seemed like wilful ill-nature, or a voluntary penance, for on these occasions it was not merely a few formal enquiries and an awkward pause and then away, but he actually thought it necessary to turn back and walk with her.

So he's voluntarily spending time with Elizabeth and going out of his way to do so.

He never said a great deal, nor did she give herself the trouble of talking or of listening much; but it struck her in the course of their third rencontre that he was asking some odd unconnected questions -- about her pleasure in being at Hunsford, her love of solitary walks, and her opinion of Mr. and Mrs. Collins's happiness; and that in speaking of Rosings, and her not perfectly understanding the house, he seemed to expect that whenever she came into Kent again she would be staying there too. His words seemed to imply it. (chpt 33)

So from Darcy's point of view, he's sounding Elizabeth out about marrying him and visiting Lady Catherine with him (this interpretation seems pretty clear given his proposal in the next chapter).

Darcy may be completely incompetent at getting across the point that he's courting Elizabeth, or Elizabeth may be completely blinded through prejudice to his courtship, or some mixture of both, but it strikes me that Darcy at least tried to court Elizabeth.