BYU fandom, or the fandom of any school. Please don't do that to yourself.
BYU joined 7 other schools in bolting from the 16-team WAC to create the MWC. TCU was happy to join the MWC as soon as they were invited.
Utah bolted from the MWC first. BYU then executed its back-up plan for independence. The MWC TV deal had always represented a betrayal to BYU by the league office. But again, TCU benefited. You are now in the Big 12.
Your situation has improved each time BYU has made a move.
I think the only time BYU fans get annoyed with TCU is when they pummel us in football, and when one of their fans comes onto a BYU message board to stir up trouble.