[EternalHope]

Why is everyone looking for personal slights, hurt feelings, or some complicated psychological weakness as the reason Clarke turned?

The most likely reasons for treason are:
1. Money. (Certainly plenty of that here, and there could easily be more than we know.)
2. Blackmail. (If Clarke has skeletons, the Clintons would certainly know about 'em.)
3. All of the above.

[Gorjus]

Why is everyone looking for personal slights, [or] hurt feelings, ... as the reason Clarke turned?

Most likely because that's the high-probability reason. The man is an ego-driven bureacrat who was shunted aside. He'd hit back regardless of money or blackmail. It's not a 'complicated psychological weakness' - or at least, it's not complicated.