I am not sure that "language only goes skin deep" is a proper use of that idiom. The usual meaning (and you're advised to look it up in an idiom dictionary of your preference) is "only on the surface", and pertains most often to beauty. So, you encounter something like his/her "beauty is only skin deep" the most.
Feelings, sentiments, meanings, cannot really be "skin deep". The author of that text perhaps meant to say that the language is only "for show", as in "they don't really mean it", there is no deep rooted belief in the hostility of those against whom such language is directed.
Edited to add: Perhaps a bit more attention needs to be paid to the fact that in the quoted passage the "language" is said to go "skin deep", which on the second thought opens the possibility that the author meant the act of penetrating rather than appearance (to which "skin deep" usually refers)...