You said that FN-2187 was with the scavenger - if his allegiance to her goes back to the events on Jakku then I see the result as this: If you had brought back the droid, they might have still tried to pursue the same plan regarding the destruction of Starkiller Base. The key difference is that the manpower you had to use to track down an escaped Force User [his face scrunches up more, even if it was his own word choice] could have been redirected to properly defend against the attack.

[He refuses to not let Ren bear part of the blame. He knows that FN-2187 played a large role in its destruction and for that connection he does hold responsibility, but it's just so fixed in his mind that this whole ordeal was a byproduct of an emotionally stunted man's poor decisions.]

Compassion was a known trait in FN-2187 before he defected, and you brought one of his people into our house. Of course he would bring the fight to our door. Surely, with your abilities, you must have felt that somehow. [so much salt, so salty]