@wintergt:
then Oda suddenly shows us that Kizaru is such a precision marksman that he can snipe a key in half from so far away.. which shows that he has been horsing around dealing crappy laser blasts all this time.
And I think that's exactly the point. Kizaru IS being leisurely about it and not taking it seriously, despite the nature of the war. Even back on Shabandy it was all just a game to him. He'd stop and watch a crazy dance attack just to see what it did. Kick Rookies around just for fun with no real intent on capturing them right then. Ride a cannonball. Use the wrong comminicator watch.
He enjoys messing around with those weaker than him, which is… pretty much everyone. And he doesn't take anything seriously, and to that end, doesn't seem to enjoy taking lives either. He's been conntet to just knock people unconscious thus far. That's just how he's been. (He was GOING to headshot Oars, because Oars just wouldn't stay down. But he seemed dismissive and annoyed that it had come down to needing such.) That he kept finding Luffy and just took the time to kick him backwards, because it amused him to see Luffy keep trying, it wasn't until what, the third time? that he actually shot Luffy down.
And on top of everything else, just because he can sprint distances at the speed of light isn't the same as his thinking and moving nonstop at that speed. (He still took a boat to get to shabondy afterall, he didn't just zip over, so he has limits) He has to turn elemental to achieve that speed. Otherwise, he walks, aims, and kicks, at normal speeds. (Or, even if he CAN move that quick, thus far he has opted to move at a leisurely jaunt at all times, so that's clearly just his nature.)