BE35 FO TAKES EXCEPTION TO ATC REQUEST THAT THEY SQUAWK EMERGENCY WHEN CONVECTIVE WX MAKES NECESSARY DEVIATIONS IMPOSSIBLE.

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AFTER A GND DELAY; WE WERE CLRED TO ZZZ OVER ABC1; AND THE STAR. TSTM ACTIVITY WAS IN THE EAST COAST AREA; HOWEVER; THE ROUTING OVER ABC1 WAS OPEN; AND OUR PREFLT WX BRIEFING SHOWED THAT OUR CLRED ROUTING WOULD KEEP US FREE OF THE CONVECTIVE ACTIVITY. AFTER DEP; WHILE PROCEEDING DIRECT TO ABC1; WE COULD SEE; VIA ONBOARD RADAR AND VISUALLY; THAT THE WX TO THE W AND NW OF ABC1 WAS DETERIORATING AND ANY OPENINGS BTWN CONVECTIVE ACTIVITY WERE CLOSING. WE ADVISED ZZZ3 DEP CTL THAT WE WOULD NEED TO DEVIATE TO THE S TO AVOID PENETRATING THE WX. WE WERE SWITCHED TO ZZZ CTR 1 MIN OR 2 LATER AND REPEATED OUR REQUEST TO DEVIATE S. CTR GRANTED OUR REQUEST. SHORTLY THEREAFTER; WE WERE ASKED IF WE COULD TAKE A TURN TO THE W. WE WERE UNABLE TO DO SO; AS THIS HDG WOULD TAKE US DIRECTLY INTO THE CONVECTIVE WX THAT WE WERE OBSERVING ON RADAR AND VISUALLY. WE WERE THEN TOLD TO TURN TO A 360 DEG HDG. WE WERE AGAIN UNABLE TO FLY THIS HDG AS IT TOO WOULD PUT US INTO CONVECTIVE ACTIVITY. CTR THEN ASKED US TO SQUAWK 7700 IF WE WERE UNABLE TO COMPLY WITH THEIR INSTRUCTIONS. WE THEN SQUAWKED 7700. ATC ADVISED THEY WOULD BE UNABLE TO WORK US INTO ZZZ1 AND ASKED IF WE WOULD LIKE TO RETURN TO ZZZ OR GO TO ZZZ2. WE CHOSE TO GO TO ZZZ1. SHORTLY THEREAFTER; ATC ASKED US TO RETURN TO OUR ORIGINAL SQUAWK. WE WERE THEN HANDED OFF TO ZZZ2 APCH. WE LANDED AT ZZZ2 UNEVENTFULLY. I FEEL THAT WE WERE ATTEMPTING TO COMPLY WITH ATC INSTRUCTIONS AND KEEP THEM INFORMED OF THE WX SITUATION. AS SOON AS IT WAS APPARENT THAT THE CLRED RTE OF FLT WOULD NOT BE POSSIBLE; WE INFORMED ATC. WE WERE UNABLE TO FLY THE VECTORS ATC ISSUED DUE TO THE CONVECTIVE ACTIVITY. IT HAS ALWAYS BEEN MY PRACTICE TO COMPLY WITH ALL ATC INSTRUCTIONS AND TO BE PROACTIVE IN DEALING WITH CHANGING WX CONDITIONS AS I KNOW ATC IS WORKING MANY ACFT AND ALL WX DEVS CAN IMPACT THESE ACFT.