That is a level of corruption way way above the typical protection racket that politicians run. They aren't just taking money from businesses in exchange for promises not to destroy them (which accounts for businesses donating to campaigns of both parties). They are taking money from special interests that have a vested interest in changing the country to something resembling a third world dictatorship.
As I already said, I think the system is corrupt, and in a perfect world, big businesses would not feel compelled to "donate" to politicians in order to buy their forbearance. But we don't live in a perfect world, do we? So we have to be realists, and choose our battles carefully.
"Perfect is the enemy of good." What that means is that if you always hold out, you refuse to support anyone who isn't perfect, then you basically hand victory over to someone who doesn't share your ideals at all and is likely to work against you. I'll take good, I'm not going to hold my breath waiting for perfect.
+1!