I don't think there's actually any inherent contradiction there: the word does still have a genuine power to shock but it does not necessarily follow that every instance of its use is shocking. Like most words, its effect depends on usage, context, intent etc. When intended offensively, "cunt" is almost always more offensive than "shit", and usually more so than "fuck". However, in informal use the word "cunt" can be sometimes be used quite inoffensively even when directed towards another person, e.g. "You won how much? Jammy cunt! Your round then?" whereas I don't think anyone would be likely to call another person a "shit" unless they intended it as an insult.