She was youth and womanhood in its most helpless and pathetic revelation.

Poor Lucy could not help herself.
She was a thing always devoured and never consumed by a flame of nature, because of the lack of food to satisfy an inborn hunger.
Horace felt all this perfectly in an analytical way.

He sympathized in an analytical way, but in other respects he felt that curious resentment and outrage of which a man is capable and which is fiercer than outraged maidenliness.

For a man to be beloved when his own heart does not respond is not pleasant.

He cannot defend himself, nor even recognize facts, without being lowered in his own self-esteem.
Horace had done, as far as he could judge, absolutely nothing whatever to cause this state of mind in Lucy.