It depends on the spirits. I'd say it's more that ayakashi can't be benign, while spirits can. But that doesn't mean there aren't dangerous spirits.

[He remembers a few particularly nasty non-ayakashi spirits among the Obon crowd, for one thing. It had been a bit of a mixed bag there between opportunistic spirits and empowered ayakashi, and neither was much better than the other.]

Shinki are supposed to be wandering spirits given a name, but I've never seen it done by a newcomer god that way.