basically i think your choice is claim RB or doctor (doctor obv wouldn't have worked) after you get claimed on OR shoot kush and immediately post flip do a "you're all gonna yell at me for not shooting vivax, i know i know, but x,y, and z yada yada please don't kill me" because in that case you're in control of the message versus shape being in control. mind you hindsight is amazing.
personally i shoot vivax and claim that shit, but it is tough. i had the same problem last game where my RB is the liability and it is tough to just cut your RB versus a goon or a GF.