What I do take issue with is the fact that I don't think my tax dollars are being used as effectively as they should be, not just because I don't feel like I get proportionate value from what they're supposedly funding, but more importantly I dont think anyone is.
I think by and large the world runs on incentives, and I don't think that the people whose job it is to allocate the resources obtained through taxes have the kind of skin in the game that's necessary to make decisions in the long term best interest of all parties involved. Anytime you have a scenario where a organization of people in society unbounded by naturally selective forces, waste and misallocation of resources will take place. It would make me feel a lot better if my taxes were going towards a system characterized by bottom up trial and errors rather than grand design, and unfortunately I think the latter best describes how our country appropriates tax dollars to our collective benefit.
As for your other question, I think there is something fundamentally fair about the concept of proportionality. I don't think its the job or role of taxation to act as punishment, because it's not as "fair" for someone making 50k a year to pay 20% in taxes to pay the same 20% as someone making 500k. I find great injustice in this idea, as I want to live in a society that seeks to empower people to become the best that they can, in a spiritual and economic sense. Not send the message that those who've achieved economic success somehow have engaged in a misdeed they have to pay or make up for.