Possible Clues:

• Vulgarian's specialty
• Lack of refinement
• Kitschy quality
• Lowbrow sensibilities
• What an offensive joke is often in
• What something tacky is in
• It's unacceptably unacceptable on the tongue
• Indecorum, e.g.
• Gaucherie
• Ordered to collect volunteers on street? It's not socially acceptable