It seems the reason you disagree with PG's article is because you're making a transgression that people who contemplate political philosophy know not to make: you've positioned economic power antecedent to political power. Specifically, that money buys votes. This is false in a democracy of any economic flavor -- though admittedly deceptive by appearance. The data is indeed somewhat reliable for those involved in political campaigns: money appears to translate to votes. Philosophers distrust this. For them, the simple requisite of having to buy votes is evidence a democracy still exists; that political power is prior to economic power. The issue then becomes the character of the voter being bought, and thus the character of the people in general.

It is easy to dismiss PG's entire article -- from its foundation to conclusions about transparency -- if you've already concluded that democracy does not exist; that votes do not translate to power in any meaningful way; that capitalism has become the real foundation on which political power is merely a simulacrum. In doing this we've hit philosophical bedrock with the shovel of pessimism, and the discussion ceases to be productive.

The law only codifies what the people, through their votes, decide to codify within it. Capitalism does not a priori codify wealth as political power. The law merely aids the confluence of capitalism: money, a signifier -- to represent resources: the signified. Capitalism is contained within the theater of democratically held political power -- until it corrupts that containment. PG's mention of secrecy in a democracy is a useful one: secrecy subverts the power of the informed voter, it is a breach of that containment. It allows the potential for capital to slip out into the realm of realpolitik -- which is reserved for the people alone through their vote.

I think if you review what PG is saying about corruption through the prism of philosophy without the distortions of politics itself (and all its frustrations) you might not consider it unsubstantiated idealism or what have you.