Tobermony Explained

The tone of the last line was dark and vengeful. Clovis felt like Appin had but so much grief and a feeling of doom on the guests shoulders, that Appin deserved being killed after he tried getting the elephant to speak like a human. The people at the party thought they were inviting someone to the party who they felt they could poke fun and laugh at. Instead, Appin flipped the situation and was there to be entertained by the other guests, who in horror, listened as Tobermony gave up all their private conversations. 

The theme is nasty people with secrets can't deal with the real consequences of their actions and hope those who brought on those consequences get what they deserve. Appin was a clever guy whose experiment surprised his onlookers more than they could have thought possible. Because of their dismay, they automatically wanted to clean everything up. Though secrets have been splattered on the wall, they thought by pouring bleach all over it, somehow all that they thought had gone wrong can be scrubbed clean. This included the perpetrators to die to hide the evidence of their embarrassment.