If we are supposed to think of general taxation and the overall amount of government spending as reasonably justified on the grounds that these things were the outcome of a democratic process which "the people" (somewhat indirectly) agreed on, doesn't the same logic suggest that the loopholes are similarly reasonable and justified?
Loopholes aren't a bug in an otherwise perfect system; they are part of the negotiating process that produces laws. If it weren't for the loopholes, legislators wouldn't be able to find support for tax rates as high as they are. The loopholes are there for a reason. The loopholes are part of the exact same "social contract" that produced the taxes.
However, the point I'm making is that once we claim the democratic process doesn't justify the taxation side due to lobbying, we also can't claim the democratic process justifies the spending side.