I seldom see much benefit in arguing about "the true" meanings of words. People have different definitions of love. What I am arguing here is that Darcy thought that whatever he felt for Elizabeth was love.

I'll also say that I don't think Darcy thought at all that Elizabeth would be hurt by the manner of his proposal, I really don't think that he consciously set out to hurt her feelings. He's noticably surprised when Elizabeth accuses him of being ungentlemanly:
"You are mistaken, Mr. Darcy, if you suppose that the mode of your declaration affected me in any other way, than as it spared me the concern which I might have felt in refusing you, had you behaved in a more gentlemanlike manner."

She saw him start at this, (chpt 34).

Lovely though love, or infatuation, is, I don't think it turns anyone into a perfect being who always considers their loved one's feelings and who always gets the feelings right. In my experience it doesn't change people's insights into others much at all. And under specific emotional stress we can become less empthatic with our partners, it's often easy to misintepret, to ignore, or to quarrel pointlessly, when our own problems absorb us. Darcy appears to be struggling most of the time with his feelings for Elizabeth and to be absorbed by that struggle internally, it's not surprising to me that it doesn't occur to him to think about Elizabeth's feelings. I am not defending him for this ignorance, but I don't think that the fact he insults Elizabeth so thoroughly means that he doesn't care for her. To me it means that his behaviour is wrong and that he hasn't learnt that he should pay attention to the feelings of others.