ACR DEVIATES FOR WX UNTIL CTLR INSISTS THEY FLY INTO CONVECTIVE CLOUD.

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WE HAD DEPARTED ATL AND CLBED TO 10000 FT OFF RWY 26L. WERE VECTORED N AND THEN TURNED E; ASSIGNED A 090 DEG HDG. WE WERE LOOKING AT A TSTM VISUALLY AND ON OUR RADAR; AND IF WE COMPLETED THE TURN TO 090 DEGS; IT WOULD BE DIRECTLY AHEAD. I ASKED DEP IF WE COULD STOP THE TURN OR CLB; AND WE THOUGHT HIS RESPONSE WAS 'YOU CAN DO BOTH;' AND HE SAID 'CLB TO 14000 FT.' WE STOPPED THE TURN ON A HDG OF 060 DEGS AND INITIATED A CLB TO 14000 FT. PASSING 13000 FT; DEP ASKED FOR OUR HDG; AND I RESPONDED WITH 060 DEGS. HE SAID; 'YOUR ASSIGNED HDG IS 090 DEGS.' I STATED THAT WE UNDERSTOOD WE COULD STOP TURN AND CLB; AND HE SAID 'NO; TURN R TO 090 DEGS.' MY RESPONSE WAS 'THAT HDG WILL PUT US INTO A CELL -- WE NEED TO GO L OR R OF 090 DEGS FOR WX.' CTLR SAID 'WE HAVE TO FLY 090 DEGS; BESIDES; I SHOW NO WX AT YOUR 12 O'CLOCK POS.' I REPLIED 'BELIEVE ME; IT'S THERE -- WE NEED TO TURN.' CTLR AGAIN SAID 'UNABLE; FLY 090 DEGS.' AT THAT POINT I RESPONDED UNPROFESSIONALLY WITH SOMETHING TO THE EFFECT THAT 'YOUR RIDE WILL PROBABLY BE SMOOTH NO MATTER WHAT HAPPENS TO US.' OUR TCASII SYS SHOWED NO TFC WITHIN 40 MI; SO WE COULD NOT UNDERSTAND WHY WE HAD TO FLY INTO THE CELL; RATHER THAN AROUND IT.