It hit me after I died for the 4th time to Super Mutants during one quest. There is no way this character could align with anyone but the Brotherhood of Steel. It just didn’t make sense. Sure, they are xenophobes. Sure, they are warmongers. However, this wasteland is so brutal and so unforgiving on Survival mode. I realized that someone who really went through this much struggle and hardship to find their child, they would not accept the synths. USURPERS really.
The Railroad does nothing to address Super Mutants. The Institute is actively trying to replace the human race! The Minutemen are good natured, but they aren’t willing to go the extra mile to do what is necessary.