Can one grow thick skin or are the thin-skinned folks doomed to take offense at everything 24/7 and attack till they die? Why?

Which one of the two do you think you are?  In the past, you've taken almost any perspective that disagrees with yours, and I quote you, as an "attack".  I'd define that as being thin-skinned. 

(Oops, is that another attack?)

Because the cry, "I'm offended!" is supposed to make the one it is said against simper and coddle the "offended" person to make everything nice again.

depends on the person, everyone is different