The Clans initially believed that the Inner Sphere had destroyed itself back to the Stone Age (something that ComStar wishes the Successor States would do (and tries to help them along with), so they could play Jesus and come save everyone from themselves). The Wolf's Dragoons mercenaries were sent to the Sphere in the early 3000's to gather intelligence on the state of the Inner Sphere. The intel they sent back indicated that the Sphere, while technologically regressed quite severely, was actually rather stable and not in fact, on the verge of total collapse.
The Clan intelligence on the Sphere cuts off rather suddenly somewhere around the 3020-3030's by order of then Khan Kherlin Ward, something that will make life difficult for Natasha Kerensky in the 50's when she answers the call to return to Strana Mechty following the death of the IlKhan.
With all that in mind, at this point in time the Clans have been isolated from the Sphere for nearly 300 years, and the culture Nicholas Kerensky devised has total hold on how the Clans operate, and as we've seen so many time in real world history, anyone who doesn't act the way you act is clearly a barbarian who must be shown the light of "true" civilisation
. While there are some Sphere residents who earn the respect of the Clans (Phelan Kell, Kai Allard-Liao, Victor Steiner-Davion and a few lesser known characters), the majority of the Sphere are still regarded as barbarians, though processes that are constantly reinforced by the Sphere's "dishonourable conduct" in battle, in the negotiation of battle, and how the Houses conduct themselves in general.
Hopefully that answers your question.