SF34 ACR PIC REJECTS LAX TWR REQUEST FOR EARLY RWY TURN OFF DUE TO TFC ON SHORT FINIAL. SF34 FLC HAD JUST ADJUSTED FLT PATH TO ACCOMMODATE WAKE TURB.

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LAX TWR CLRED US TO LAND BEHIND A B757 AND ADDED; 'CAUTION; WAKE TURB.' AS PER OUR FLT MANUAL AND THE AIM; WE FLEW ABOVE THE B757'S GLIDE PATH AND LANDED BEYOND ITS TOUCHDOWN POINT. AS I WAS LOWERING THE NOSEWHEEL TO THE GND; THE TWR HURRIEDLY SAID 'CAN YOU MAKE ONE OF THE HIGH-SPDS?' THE FO; REACTING TO THE IMPLIED URGENCY; REPLIED THAT WE WILL MAKE TXWY K. I IMMEDIATELY SAID NO; AND THAT WE WOULD MAKE TXWY M. THE FO INFORMED THE TWR. THIS WAS IMMEDIATELY AFTER HIS FIRST REPLY. I BRAKED AND PULLED THE PLANE ONTO HIGH-SPD TXWY M; ON THE R SIDE OF RWY 25L. AS WE WERE XING THE LINE THE TWR SAID; 'TURN OFF L ONTO A7.' THIS WAS IMPOSSIBLE TO DO QUICKLY AND WE HAD ALREADY JERKED THE PAX AROUND. THE TWR; SEEING WE WERE ALREADY ON TXWY M INSTRUCTED US TO PULL UP AS TIGHT AS WE CAN BEHIND THE FIRST ACFT. A MIN LATER THE TWR SAID TO US THAT 'WHEN WE TELL THEM TXWY K; THEY PLAN ON THAT.' WE REPLIED THAT THEIR REQUEST WAS TOO LATE. THE REASON FOR THE TWR'S PANIC WAS THAT THE PLANE BEHIND US WAS TOO CLOSE. THIS PLANE; WAS ON A VISUAL APCH; AS WE ALL WERE. SEPARATION IS THEIR RESPONSIBILITY. THE TWR SHOULD HAVE EXPECTED OUR COMPLIANCE WITH WAKE SEPARATION PROCS AFTER THEY HAD ISSUED US THE WARNING. FURTHERMORE; IN THE PERHAPS 2 SECONDS BTWN THE FO'S 2 REPLIES; THE TWR HAD NO TIME TO PLAN ANYTHING AT ALL; BUT TO HOPE THAT WE COULD SAVE THEIR DAY. IT SEEMS THAT LAX TWR ISSUES THESE WAKE TURB WARNINGS OUT OF HABIT; BUT WITH NO THOUGHT AS TO WHAT THIS REQUIRES OF THE FLC'S.