When someone accuses you of having bad ton, they are intimating that you have recently crawled from beneath a slimy rock located in the outskirts of Society and should most likely stay there as you have no clue how to adhere to the rigorous standards of having your brain washed in mainstream society and your ignorance might be contagious.
Ton derives from the French phrase Le Bon Ton meaning good form. It originated during the Georgian Era when the fashionable thing to do was follow the social leader and never allow an original thought enter your head lest you be branded an outcast from society. Mindless conformity at it's best.
"Who's Taylor Swift and why does she hate Kanye West?"
"You're kidding, right? That's bad ton."