Robert Brandom sees Kant and Hegel as both working to reconcile the modern notion that normative statuses depend on normative attitudes with a genuine bindingness and objectivity of normativity. The key point that he associates with modernity is the idea that normative statuses are not somehow pre-given. As I would put it, the normative statuses of things depend on complex reflective judgments involving many elements.
Brandom’s language about attitude-dependence is intentionally broad enough to encompass all the forms of modern subjectivism, which is the opposite evil to traditional groundings of normative statuses in pure deliverances of authority. At its most primitive level, it expresses the idea that everyone judges for herself, which is indeed a popular sentiment in modern culture. Expressed this way, without qualification, it makes it impossible to separate right from wrong. Brandom seems to want to say that even this vulgar subjectivism or voluntarism is historically progressive compared to the traditional “authority-obedience model”; I tend to think they are equally bad.
The real positive lesson that Brandom extracts from this, though, is something to the effect that everyone deserves a seat at the table in inquiries about the good. He does not himself support the view that everyone gets to judge everything for herself.
Indeed he points out that the very best version of this individualist view — Kant’s theory of the autonomy of moral subjects — is criticized by Hegel as one-sidedly individualistic. Kant complements autonomy with a strong emphasis on respect for others, but according to Brandom, Hegel also thinks that Kant effectively treats both autonomy and respect as principles that themselves do not depend on any normative taking of things to be such-and-such; i.e., at a meta-level Kant still treats autonomy and respect as the same kind of givens that he recommends we avoid depending upon in all our particular judgments. With his theory of the coming-to-be of genuine objective oughts through processes of mutual recognition, Hegel is able to show a genesis of autonomy and respect, as themselves instances of the same kind of normative taking involved in particular judgments.
I’m not completely happy with Brandom’s choice of the thin term “attitude” in this context. I would prefer to say, for example, that normative statuses depend on reflective judgment. Attitude by itself says nothing about its derivation; an attitude just is what it is, and might be entirely arbitrary. But I suspect that Brandom implicitly has in mind something like a complex propositional “attitude”. Then on his view of what it is to be a proposition, necessarily we are in the space of reasons, and subject to all of its dialogic give and take, just by having such an attitude.