A seemingly neutral phrase like 'colored people' that once was acceptable to pretty much everyone can become offensive over time. You can say the same thing about other words or phrases that once were used to describe people of color. The process involves other words or phrases becoming popular and more preferred by people of color until it starts to be noticeable that the people 'not of color' who continue to use the old terms are largely insensitve, or at least somewhat clueless, to what the people being described prefer to called. Eventually it starts to feel kind of insulting, and people not members of the described group start to be viewed as intending insult when the old term is well past its expiration date.
I'm not anti-Christian. I'm anti-stupid.
