Does he accept no campaign donations? Does he never meet with lobbyists? What do you think that is?

Having a direct financial interest is not the only reason someone can propose bad legislation. Politics run on favors and negotiations. I might not be bought off by an outside interest, but I might owe one to my friend, who might owe one to his friend, who turns out to have a deal with the outside interest...

Reputations are good until they're not. People are fallible and there plenty of examples of politicians who have a public image and a backroom one.

I don't know Peskin and there are many honest hard working politicians, but safeguards like disclosing conflicts of interest aren't terribly burdensome for good politicians but can help generate legal consequences for the bad ones.