But buffet is the one saying he doesn't pay enough in taxes. If he wasn't hypocritical then he has means to do something about it. He can maximize his taxes, he can write them a check for as much as he wants, he can say that his entire estate is going to the government instead of the Gates Foundation. It's hypocritical to talk about not paying enough taxes and not doing something when you can. People on here support bigger government problems, complain about how the teachers don't have enough money, etc. Then do you your part too, pay more in taxes.
Your analogy breaks down pretty quickly. Buffet's point is that the taxes on people like him in comparison to his secretary are too low. There is no reason to pay more in taxes if no one else in your situation is going to pay more, since any particular individual's contribution is not really going to address the total problem.
There is nothing hypocritical in advocating for more government spending (in total) without addressing the funding mechanism. There is nothing necessarily hypocritical in advocating for more gov't spending and a specific funding mechanism that does not affect you.
For example, I don't mind paying more in taxes to support education. I do mind paying more in taxes to support education if I am the only one doing so, or if there are others who I think also ought to paying more.
Another example is the progressive income tax. There is nothing necessarily hypocritical in advocating for a more progressive income tax system to fund some project when advocate is unaffected if the rationale is that a more progressive income tax is a good thing for society.