A lot of girls who have had bad experiences with a certain race or just simply does not feel an attraction towards that race will sometimes turn away a client at the door making some stupid excuse/ watching them buzz in the security camera and not open the door for them/when can see them from their incall that a client has parked and ready for the buzzer and apartment number will just simply not pick up. All this happens because she decided to not specify in her ads that she will not see a certain kind of race due to bad experience/ has a lack of attraction towards that race.
There is a lot of ways to get a point through one of them being crude and the other being being upfront but polite. A statement like "White is right" in my opinion is trashy and racist and speaks a volume of how the person thinks. A lot of sps don't like seeing clients of their own race not because they hate their own race but because it just simply makes them uncomfortable or she is in fear that she might bump into someone from her own community and if not the word may pass around. An sp has the right to choose and most of them will base their decision to see a client depending on their mannerisms over the phone, general etiquette and hygiene.
By posting a crude racist remark like that she may lose a lot of potential clients but may as well gain a few like-minded clients.
One thing however I would like to add in her defense is that she may simply not realize that what she is stating in her ad is in fact racist- she may be ignorant or just too oblivious. Also communication does get lost in text- different people with different kinds of personalities will interpret it differently, as well as none of us can really know for sure what was going on in her head when she wrote something like that or does this girl have a odd sense of humor that usually may offend people (there are people like that in all our lives and we learn to love-hate them). A friend of mine constantly makes sexist comments about how women should do this or do that and how men can do everything they want or are more powerful then women. We argue every time and being the logical thinker that I am (well majority of the time unless I become overly emotional and lose all sense of thought lol), I usually win all these arguments and with time does it really change his opnions? No it does not, he continues to make these comments in conversations and over time I have learnt to let it go. Some people's nurture is stronger than their nature. When you have been brought up around a thinking style it is hard to let go off it as an adult- because when you do you end up confused, but thats courage to open ourselves to different opinions.
Since the girl is native I want to add something. A lot of the native population are brought up oppressed, some are a mix of white and native and get lost in the limbos. They have a hard time finding their own identities. They growup thinking white is better and being white is right, because the circumstances around them ingrains that schema in their minds. There is a Canadian book called "Celebrations", it talks about the second world war and the role the natives played in it and how they were treated as disposable commodities once the war was over. How the protagonist felt lost because he was a white and native mix. He near the end embraced one of his cultures to finally belong somewhere and help himself to adapt an identity that is unique to himself only.
Growing up in a culture where being darker skinned I was sometimes not considered to be pretty. Lighter skin girls no matter how they looked or had totally botched up features were still considered pretty because they had lighter skin. When a baby is born in the family everyone raves about how "fair" the baby is. When caucasian people where seen on the streets( very rare), little street kids would follow them around, people would stare, point and smile- kids would run to their friends to get them to see these fair skinned people. Even once my dad was driving me to school and he was waiting to turn onto a lane and he kept on honking and getting mad at the local drivers who wouldn't let him pass and finally this one white man in his white toyota with diplomat number plate finally stopped to let my dad pass because it was his right of way, my dad's facial expression changed and he smiled and gestured the guy to please go first and he would wait. Till today I wonder did my dad's attitude change because he was white? or was it because he appreciated that the guy followed the traffic rules and was polite enough to stop?
I know racism is something in this day and age is hard to digest and is unacceptable but sometimes it helps to try and see it from a different perspective. If we really want to eradicate racism (which imho will never go away completely/ will come back in some form or another), we have to fix the roots to the problem before we can expect a perfect tree to grow

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Sorry for the long long post