It's not at all hypocritical, as long as he pays that new higher (but minimized-by-army) tax burden, should it actually go through. That's like saying an NFL cornerback who liked the old "push out" rules shouldn't try to push receivers out of bounds before making a catch, as is permitted with the newer rules. You can argue for different rules while playing the game with the rules that are actually on the books.
Warren Buffet's personal income tax rate is not a competitive sport. It only affects his take home pay. I could kind of see your analogy holding for the taxes his company pays because they have to compete with other companies. But I believe Buffet is arguing for a higher personal income/capital gains tax rate. See: http://www.nytimes.com/2012/11/26/opinion/buffett-a-minimum-...