http://en.wikipedia.org/wiki/Anti-imperialism
Ah, I get it, now. It's another way of calling him a Marxist.
However, I would like to point out that being an "Anti-colonialist" does not necessarily make one a Marxist or even a mild leftist. Ron Paul has spoken out against our government engaging in empire building. Libertarianism contains an element of anti-imperialism.
Heck, if you think about it, this country was founded by men who opposed and successfully fought colonialism, gaining independence from a powerful empire.
If I were Obama, I would have stated my pride in being an anti-Colonialist and citied the above example. That would have been a nice middle finger in old Newties face.
Dave