Obama did not simply happen to encounter a lot of people on the far left fringe during his life. As he spells out in his book, he actively sought out such people. There is no hint of the slightest curiosity on his part about other visions of the world that might be weighed against the vision he had seized upon.
As Professor Richard Epstein of the University of Chicago Law School has pointed out, Obama made no effort to take part in the marketplace of ideas with other faculty members when he was teaching a law course there. What would be the point, if he already knew the truth and knew that they were wrong?
This would be a remarkable position to take, even for a learned scholar who had already spent decades canvassing a vast amount of information and views on many subjects. But Obama was already doctrinaire at a very early age -- and ill-informed or misinformed on both history and economics.
His statement in "Dreams from My Father" about how white men went to Africa to "drag away the conquered in chains" betrays his ignorance of African history.
The era of the Atlantic slave trade and the era of European conquests across the continent of Africa were different eras. During the era of the Atlantic slave trade, most of Africa was ruled by Africans, who sold some of their slaves to white men.
European conquests in Africa had to wait until Europeans found some way to survive lethal African diseases, to which they lacked resistance. Only after medical science learned to deal with these diseases could the era of European conquests spread across sub-Saharan Africa. But the Atlantic slave trade was over by then.
There was no reason why Barack Obama had to know this. But there was also no reason for him to be shooting off his mouth without knowing what he was talking about.
Similarly with Obama's characterization of the Nile as "the world's greatest river." The Nile is less than 10 percent longer than the Amazon, but the Amazon delivers more than 50 times as much water into the Atlantic as the Nile delivers into the Mediterranean. The Nile could not accommodate the largest ships, even back in Roman times, much less the aircraft carriers of today that can sail up the Hudson River and dock in midtown Manhattan.