What else could they do? Sitting in silence would have been worse, but talking with a young man he had seen as a snot-nosed, arrogant brat who he was attempting to treat as somewhat more of an equal... yet there would always the age difference, one that he wasn't entirely certain Draco would respect.

Give it a go, though.

Still, he gave real thought to Draco's question, frowning as he turned over what best to say before starting hesitantly, "...a Patronus... is a spell that is unique. Not every wizard will be able to perform it, even if they are powerful. It is a deeply personal spell, unlike most. You're right, you were raised around dark magic," he wouldn't put that nicely, "but you are not your parents. We each chose our path in life, and your path is not necessarily as dark as your parents."

He met Draco's eyes, brows lifting slightly. "As proven by your casting of the Patronus. However," and here his voice went soft, "if you were to chose to follow the path they had walked before, you would lose the ability... or worse." He was a bit more grave on the last two words.