It's not that politicians are uniquely corrupt, it's that a system pf political power uniquely corrupts the people who are in it.
I would argue that to suggest otherwise is to suggest that incentives don't affect how people behave, their ethics, or what they believe. Which I would certainly disagree with.
I agree with you on the earlier point, that no individual is inherently trustworthy, which is why I'm far, far more skeptical of hierarchies of unaccountable, bureaucratic political power in a general sense. I think they reinforce exactly the sorts of corruption and malicious intent that you are claiming we need to better protect ourselves from. On which I agree, but seem to disagree on what means we have to prevent them, and what systems help or hurt that cause.