Yes they can be. The worst racism I ever encountered while living in Southern Africa came from White South Africans.
When travelling in South African we got quite a few lifts from White South africans. One in particular still sticks in my mind ot this day.
The girl I was travelling with worked in an SOS Village in Harare. She was the only white member of staff, and all the people living at the village were black. I on the other hand worked at a very multiracial school.
While travelling down to Cape Point in the back of a pick-up truck (with our bikes chucked in there with us). The couple (also sat in the back) asked us if we worked with Black people. Both of us said yes, and my friend elobrated saying how she was the only non-black person there.
They were visibly shocked and one said "and you actually want to work there, I couldn't possibly work somewhere with no white peole, and take orders from a black man". We were both speechless and spent the rest of the journey in near silence.
On the other hand, we met some absoultey WONDERFUL South Africans while travelling out there. Friendly, courtieous and welcomed us with open arms.
And all of our suppliers (atm) are South Africans, lovely friendly people. Oh and the assistant houseparent when I was at school was a South African. Lovely lady,although I remember at first she did seem rude/dismissive but (as with many parts of the world) understandings/reactions to different situations vary and once she adapted we all loved her