Abuse survivors, and especially survivors/victims of domestic violence often keep up extreme public and private politeness as a matter of safety, however. Speaking back feels deeply unsafe in all circumstances. It can lead to harm. Their politeness is an artefact of abuse and a protective mechanism, not an artefact of privilege. Domestic violence crosses all ethnic, class and cultural boundaries.
It isn't a simple issue and there are some people who are caught between two fires in this debate.
I absolutely support the right of those who are subjected to abuse, oppression, elision and exclusion to shout back, to push, to demand. This is not an area in which there can be compromise.
But there are also people of all races and backgrounds for whom this option is never available and they may speak and act as they do because it is their only safety.
You may now drop the internet on my head.
Edited to add: an excellent discussion of abuse victims/survivors and psychology by Lois McMaster Bujold here -- http://lists.herald.co.uk/pipermail/lois-bujold/2013-January/116928.html Thanks to mmegaera for the link.