This depends a great deal on what you call equitable. Some people think that it is equitable that Mitt Romney appears to pay a lower percentage of his income in taxes than Newt Gingrich does because Romney's income comes from different types of sources. Others think this is inequitable. It is all in the eye of the beholder.
My opinion is that our system is not equitable because it is riddled with loopholes and special tax breaks given to those who have political clout. We should have a system that is more simplified and does not give all sorts of tax breaks to people and corporations that do not need them. I also think that our system is somewhat more regressive than it should be because of the fact that Social Security taxes are not taken from earnings above a certain level.
Overall, our system is not horribly unfair, but I think that it tends to help the politically powerful more than it should.
I also agree that it is objective. To the elite of this country, taxation is extremely equitable. As mentioned above, they are allowed many loophholes, but there are many more ways in which elite coroporations gain from taxes.
Elite bankers, for example, can perform criminal acts as seen in the derivative market and get bailed out. Meanwhile these same banking cartels control our currency through the privately owned and unregulated Federal Reserve. While many believe the Fed to be an arm of the government, nothing could be further form the truth. In fact, the US government has no oversight over the Fed. The Fed is essentially a debt creation tool where they can print money from thin air. This money is then lent back to the goverment with interest creating trillions in debt and ensuring an increase in inflation.
It is socialism for the elite and capitalism for the rest of us. So, unless you fall under the 1% of Americans, taxation is not equitable.