Thought-terminating cliches

A thought-terminating cliché is a commonly used phrase, sometimes passing as folk wisdom, used to quell cognitive dissonance. Though the phrase in and of itself may be valid in certain contexts, its application as a means of dismissing dissent or justifying fallacious logic is what makes it thought-terminating.

• "Whatever."
• "We will have to agree to disagree."
• "I'm just sayin'."
• "Such is life."
• "Think about it."
• "God works in mysterious ways."
• "Love it or leave it."
• "That's a conspiracy theory."

Many more examples at Wikipedia.