Humans are fundamentally irrational creatures. The divide you speak of is not due to genetics or 'race', at least in my opinion. It's due to knowledge and experience. Rationality is learned and acquired. I suppose it might be like a skill.
Now, it may be true that some people are less capable of rationality than others. But that isn't a racial divide. It's no different than some people being fundamentally better at math, or reading, or whatever.
By the way, not everyone "makes a decision" to be irrational. Indeed, I think it's far less likely than that radio show suggested. I know that I've never made a 'decision' to lose my temper, for example. I think it's describing the after-the-fact rationalization process that people undergo to explain why they do things. For example, I recently lost my temper (the circumstances aren't very important), and without thinking at all clearly, I decided to leave and go back home. Once I had calmed down (at home), I realized that it was getting that distance that allowed me to calm down - I would have stayed angry if I had stayed there. But I didn't decide to leave to get that distance, I decided to leave because I was pissed off and fed up with the situation. It wasn't just me quietly leaving - I announced it and made a small production out of it, as a way to further express my anger. A petty, irrational decision, in other words.
But after I had calmed down and was sending text messages to explain, I put it as "I realized I needed space and time to avoid getting further upset". Which may have been true, but it certainly wasn't something I consciously or rationally decided at the time (and yes, I have trained myself to manage my temper - this was the first time in a while that I'd lost it). Frankly, I doubt most people have the presence of mind when caught in the sway of powerful emotions to make rational decisions - and the ones that do learned how to do it, either accidentally or by example.