What the 7th Sea GM's Guide recommends doing if you have mood ruining Players is to place a bowl of white dice in the middle of the table. You tell the player's that this bowl contains Karma Dice. Whenever a character is about to get killed by a villain or henchman, any play may pull a die out of the karma bowl to save that character's life.
Now here's the key. Whenever a player does something to break the mood. Like make Python reference the GM is supposed to throw a BLACK die into the bowl. The Guide suggests that the GM shouldn't tell the players what that's for. Then whenever a player (preferably the player who made the comment but not necessarily. There's nothing better to have players help you keep another player in line if you screw over someone ELSE for their goof off.) does some really heroic act that thwarts or kills the villain, you pull out one of the black dice and say, 'Um, no, you fail.'
John Wick is evil and doesn't take sh*t from his players. Don't get me started on COWARD dice.