Is it best not to mention a denomination or branch when talking to a person who belongs to a different one? I learn that it is best to avoid talking about politics with others, because people holding different political views can easily become hostile towards each other.

As an Atheist, I was wondering a similar question: when talking to people of a denomination or branch, is it generally better to avoid mentioning other churches of different denomination or branch?

I am asking about rule of thumb, and it is not uncommon to meet people of 


Protestants and Catholics 
Within Protestants,  Presbyterians, Methodists, Baptists, ..., 
within Presbyterians, Methodists, or Baptists, there is also distinction between Mainline and Evangelical.
Unlike politics, Christians of different denominations very rarely are hostile to one another. The differences between denominations are not very significant in everyday life. Most Christians have close friends different denominations and many would be hard pressed to articulate the differences between their denomination and any others they might encounter. Even when they are known, the differences are rarely a cause for animosity and it is safe to talk about denominations.

There are a few parts of the world where the above is not true but those cases should be easily identified.