Oh, Marigold!" Lymond spoke plaintively. "A silken tongue, a heart of cruelty. Don't berate us. We're only poor scoundrels-vagabonds-scraps of society; unlettered and untaught.
"Oh, Marigold!" Lymond said sadly, expressing his feelings about her. He describes her as having a charming and persuasive way with words, but also a cruel heart. He seems to be pleading or lamenting her treatment of them.
He then defends himself and others like him, calling them poor, rebellious outsiders of society who lack education and refinement. Lymond implies that their actions are shaped by their circumstances, not by malice or intention to harm others.