Bronlie (or Bronly) is a perjorative term used to describe fans who value Sam and Dean above all others and resent any second of the show spent with other characters. The term is a mashup of Brothers Only and plays on the term Bronies which is used to describe male fans of the My Little Pony animated series.
Most but not all Bronlies also ship Wincest. This group tend to be particularly vitrolic towards Castiel, usually refusing to utter his name and referring to him as TGDA (That God Damn Angel). They are engaged in an endless and bloody war with Destihellers.
The Venn diagram of Bronlies and Tin Hats is a circle.