At the very least, John Constantine seems to know when to let it rest. Angels, apparently - or any questions surrounding this specific angel that he's associating with - are off limits. That's a sore price to pay, considering heaven and angels are the things that Castiel is, unsurprisingly, most curious about, but free will.. it sure is a bitch. He can force the answers out of John all he likes, but he doesn't want to, it would chafe his core values too deeply, but here John is all but agreeing to answer anything else, and beggars can't be choosers.

Castiel sighs, in that long suffering sort of way, squinting out at the road ahead.

"You still haven't told me why you're doing it. Why you're hunting demons."

Hunters are easy enough to figure out - they hunt because they know there are creepy, crawling things out there that go bump in the night and eat children for breakfast, or they do it out of revenge, because a werewolf mauled their husband, or a vampire turned their daughter, or a demon burned their home and family to a crisp. Most don't tangle with demons, however. The Winchesters are a bit of an anomaly, special in more ways than Castiel can rightly describe, and even still, they don't consider themselves 'specialists'. They don't hunt demons in particular, they hunt everything. That John chooses this singular, far more dangerous prey is.. interesting, and telling.