Mat block is essentially like protect but with a wide defense of a team. Your greninja who can learn mat block, could be placed anywhere on your team and still block all three allies (or two for double battle). It's a really great move! The only problem, since it's so powerful/useful, it would not work every single time you activate it. You might want to switch the roles back and forth with mat block and other attacking, defending, or status moves.
But, dealing with your situation, I don't think you can hit your team with it. If you want to active anger point, you should give your tauros a focus band or focus sash. Therefore, your opponent can't finish you in one shot - having a high probability of activating your ability. I don't think attack your ally is the best, since the opposing team could finish them off.
But, it's your decision!
Hope this helped! Please like if helpful :)