...if silence would imply...

Expressing offense and feeling offense are correlated but by no means identical. One can very easily do one without the other. I'm uncertain which of these interpretations this fact comes down in favor of.

However, it seems like feeling (and to a lesser degree, expressing) offense (in most cases) is inspired by, "It's just wrong for you to say that and you must be chastised!" rather than by, "You made an implicit assumption about me that I find offensive, and you must be corrected!" Offense feels a lot more like "They broke the rules!" than "They lowered my social status implicitly, kind of!"

I see no problem, for either model, coming from the abolitionist/fire-eater example. If you're an abolitionist, you believe "Slavery is very bad." If you're a fire-eater, you believe "Slavery is very good." Believing the opposite would lower your status in your peer group and it threatens the social order you desire (even if you haven't established that order as a standard for society, it is the standard you believe society should operate by). I don't see the latter as being much more "elaborate" than the former.

Althought, when two people of opposite political viewpoints argue a contested issue, I think they experience anger much more than they experience offense. They may incidentally offend each other along the way, but I think anger is the dominant feeling, which makes sense, because it's a lot like an actual fight, mentally.