First off this is all just empirical. Don't quote me. By low-level I mean instinctual, basically what animals do. Intelligence significantly involves being able to delay gratification so you have some space to reason, think without having to take immediate action, or respond to how something first seems. Longer-term planning (like surviving through a winter) requires intelligence. So my off-the-cuff theory is that intelligent people, going on some ideas or ideology, could think it's good to suppress empathy in some cases.