Another Attempt to be Fair
Obviously a great many powerful people have an interest in preventing a rise in the tax rate for the very wealthy, but interest doesn't explain all the opposition. It’s important to recognize that much of the passion on the right reflects principled belief. Opposition to tax reform, indeed opposition to the very idea of a graduated income tax, follows inevitably from an absolutist view of property rights. By the lights of that way of thinking, taking 38% of income over $250,000 a year instead of 36% is just as bad as stealing somebody's horse. What makes the right wing even more strident about all this is the meta belief that the validity of their way of thinking is self evident so that anybody who disagrees is either feeble minded or evil—a whiff of John Calvin hangs in the air around many a conservative, especially the Southern ones.
The idea that property is a social construction, that what's mine is mine because the rest of you agree to recognize that it's mine, is worse than newfangled rubbish or recycled Marxism. For many conservatives, it's utterly alien, the ideology of Cthulhu. I think you can complain that the outlook of the right is both ahistorical and unrealistic—capitalism just doesn't work without some mechanism of redistribution—but it's neither fair nor useful to chalk up all the opposition to self-interest.
By the way, if I’m right about all this, it follows that the Republicans we can do business with are most likely to be those for whom opposition to changing the tax code is simply an exercise of greed. You can reason with the insincere.