While I think we generally agree that the concept of triggers is WAY overused in the younger generations, I can see a few situations where a "timeout" or "this is more than I can handle" concept is totally valid.
My first thought was if RPGs were being used to within the scope of treatment of PTSDs. A novel concept which I was not sure existed, but of course the GREAT GOOGLE provided
http://rpgresearch.com/blog/rpg-for-...ya-interview-1
As with everything in life the concept of a timeout in an RPG is a tool which can be used in many different ways. It might be used by someone with genuine psychological issues to feel safer in exploring their own "danger zones", or it could be used to impose a minority opinion onto a larger group by allowing one person to dictate what is acceptable speech.
The choice on if the tool has merit and how it should be used should be left to each gaming group. My hope is that most groups would like to push their own boundaries and try to be uncomfortable in a way that makes them think, but to each their own.