My parents won't let me play zombie games.?

So my dad will let me play most M games except for GTA but the annoying thing is i can play black ops zombies but whenever I ask him if I can buy Resident Evil/Left 4 Dead 1 & 2/Dead Rising. He will say oh its too gory or disgusting.... He let me get black ops and gears of war.... ( Also please don't respond with the "Practice Being more mature" answer you would be surprised how noneffective that would be seeing how I already am quite mature. So please help me out!