I don't even know if I'm touching the subject you're hoping to discuss, but here are some of my thoughts that I think are pertinent:
Why a Liberal may over-shoot a Conservative:To a Liberal, being "bigoted" or "set-in-your-ways" or other such things is a horrible, horrible thing. Therefore, when they characterize someone who is seen as those things... they think of them doing horrible, horrible, extreme things.
Why a Conservative may under-shoot a Liberal:If a Conservative is accused of being "bigoted" and "set-in-their-ways" over and over again... however, they still live their lives relatively the same as any liberal does (going to work, caring for family, friends, being nice when they can, losing their temper sometimes, feeling bad about losing their temper...) they're going to understand that being called "bigoted" doesn't really mean you're an extreme-horrible person. Therefore, even though a Conservative may think of a Liberal as "bigoted" in their own way... they will understand that "being bigoted" doesn't have to be quite as extreme as some Liberals may think it is.
I dunno if that even makes sense.
Anyway, those are my thoughts for the day.