Probably not a racist, at least meaningfully more so than his contemporaries. Let's remember that what he had were trained, disciplined regular troops against certainly fierce and brave but ultimately irregular tribal warriors.

Want to ask the Romans how much straight military arithmetic actually matters in those equations ? 'Course it was a bit different with firearms involved, but still.

I've gotten the impression his main bungle was not realizing in time that the other column had been thrown back and the Indians were now moving against his suddenly very lonely command en masse, and in a rather bigger mass than he'd anticipated too.

'Course, he might also have been plain caught off guard, panicked and started making very stupid decisions. That's nothing particularly new in warfare.