Racism? Sexism? 'Differentianism'?

'Science Blogs' was one of the blog packs that came with Google Reader when I signed up. Being a research-hobbyist, I read the pack almost as much as my friend's.
Cognitive Daily is one of the more interesting blogs in this pack and recently had an article discussing a research on Racism.
They took a group of people and while they were speaking on video conference 1 to 1, monitored their anxiety level. In one scenario, there was a deliberate 1 minute time lag and in another there was no time lag.
They found that when the people talking were of the same race ie white-white/black-black, the anxiety levels reduced when a time lag was induced in their video chat. However, in a mixed race scenario of white-black, the anxiety level actually increased.
Implications are profound considering the recent date of the study. Most people believe and will get very offended if they are called racist. But, then why is there an underlying mistrust with interracial conversations?

Someone suggested that this is 'differentianism'; anyone different from you should not/can not be trusted. This could go on a long way to explain sexism, religionism and even castism. One example Vinit gave which expats or NRIs notice is that living in the same country, white/blacks may have issues. However, send them separately to India or Vietnam and they will tend to cling together- cause now a bigger difference has arrived and after all they are of the same country/culture. The same can be applied to Pakistanis and Indians going to another country. At home, they might have many differences but amongst people with a different outlook on life, they just become 'Desis'.

According to Vinit, this could be explained by the history of humanity. According to National Geographic, humanity at one point had almost died out and had a population of just 4000. To survive that, people must have had to compete for the same meager food resources; thus bringing about our inherent distrust of strangers and people of 'other tribes'. A lot of conquests in our early history were carried out for survival of the tribe.

If you follow the gene lines created by Genographic Project, the Y chromosome line are significantly different from the mitochondrial DNA lines. Most of us are the product of armies of men coming into a region, either settling down or impregnating women and moving on (which? we don't know). This might even, shed some light on the different natures of men and women, men being more competitive on the whole. Women do seem to vanish when a field becomes very competitive even if they were amongst the initial pioneers- IT being an example.