Google of course must give users the option of selecting and/or recording their own activation phrase and/or password phrase. Even given the option, most users won't bother to set that up.
So Google should give allow users to say "Block Burger King", block "Whopper", etc. to block specific voice activations.
Let Burger King play their harmless and educational trick.
When users get disgusted, they can block it. BK loses in the long term. They and other actors will then have to decide whether future exploits like this will do more harm than good.