Why was the lawyer embarrassed?

From the text:

To be sure it is a singular tale; and the explanation is one that I blush to have to offer you. For," says he, really with embarrassment, "the matter hinges on a love affair."

"Truly," said I, "I cannot very well join that notion with my uncle."

"But your uncle, Mr. David, was not always old," replied the lawyer, "and what may perhaps surprise you more, not always ugly. He had a fine, gallant air; people stood in their doors to look after him, as he went by upon a mettle horse. I have seen it with these eyes, and I ingenuously confess, not altogether without envy; for I was a plain lad myself and a plain man's son; and in those days it was a case of Odi te, qui bellus es, Sabelle."