The fact that self-interest may play a role in the careers of many politicians doesn't undo the damage that this attitude has caused to our polity.

"They're all fuckers, they're the same" is the attitude that leads to people being unable to differentiate between one party that is subject to excessive corporate lobbying and donations, still starts too many wars, and frequently makes mistakes but nevertheless is fundamentally trying to improve most people's lives, and another that wants to destroy Medicaid.