This expression is a truncated version of the longer and more widespread phrase be like a pork chop in a synagogue; this has been around since the 1950s. Since pork is forbidden food for Jewish people, to describe something as being like a pork chop in a synagogue means that it is highly inappropriate, embarrassingly out of place, and quite unwelcome. The Australian expression carry on like a pork chop has now shifted the focus from inappropriateness to foolishness. (Often happens with truncated expressions — they kind of go their merry way!)
'Porkchops CANNOT be ginos; it's as simple as that.'