Jorgen Modin has archived on his site Wikipedia’s now deleted page on Thought terminating cliché:
A thought-terminating cliché is a commonly used phrase, sometimes passing as folk wisdom, used to propagate cognitive dissonance (discomfort experienced when one simultaneously holds two or more conflicting cognitions, e.g. ideas, beliefs, values or emotional reactions). 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.
There are a wealth of examples that you will be familiar with, including “Everything happens for a reason”, “Don’t judge”, “Ah well, swings and roundabouts”, “To each his own”, “Life is unfair”, “You only live once” (YOLO), “We will have to agree to disagree”, “You just don’t do that”, “Rules are rules”, “I’m just sayin’” (which I actually use a lot — sarcastically!) and one that always makes me angry: “Because that is our policy.”
The ex-Wikipedia article also cites some religious examples, like “The Lord giveth, and the Lord taketh away” (Job 1:21), “The Lord works in mysterious ways” and “God has a plan.”
The article observed that The statement “that is a thought-terminating cliché” can itself function as a thought-terminating cliché. Once the stator has identified a first statement as a thought-terminating cliché, they may feel absolved of needing to determine whether that first statement is indeed a thought-terminating cliché, or provides useful insight, in the context under discussion.
In fact, it appears that rather than delete the page Wikipedians decided instead to merge it into the page on Thought Reform and the Psychology of Totalism, the non-fiction book by psychiatrist Robert Jay Lifton that popularised the term.