Leo, if you follow the link trail you get to the science journal:
http://psr.sagepub.com/cgi/content/abstract/14/1/126
It apparently was a meta-analytical study, which generally tend to make me raise my eyebrow, however I have heard of other studies that come to a somewhat similar conclusion, so yeah, I believe it. But as Padraic pointed out, correlation does not equal causation and it would be interesting to see if there is a causal mechanism that triggers racism and religiosity.
One study, which was discussed at length on Reasonable Doubts, attempted to study latent racism. Since it's not socially acceptable to be racist, a lot of it is hidden in actions and code words. Anyway, this study had people took a survey about religion and then they were asked to to see a movie to study for some made up reason. They had a choice of two rooms, one with a white guy and one with a black guy. Sometimes they would be told the movie is the same so it doesn't matter which room they choose, or that the movie was different and they could choose the one they preferred.
The findings showed that people who were more liberal in their religious beliefs would choose to sit next to the white or black guy with a rate that was statistically insignificant.
What was interesting was the more fundamental people significantly chose the white guy when they had a choice of the movie and could hide their choice with like or dislike of a movie. When the movie was the same they significantly chose the black guy so as not to appear racist. Granted it's hard to specifically say why a person was making the choices, but the statistics were such that was beyond noise. I wish I knew the name of the study so I can post it here. I'll have to try and look it up when I'm not too busy.
Anyway, I think that a part of the reason religious people might be significantly more racist is that when you're believing things on dogma and faith, already you're thinking uncritically, and with that lack of critical thinking it's more likely you would accept things like "Whites are superior" etc...