Harlan Palmer seldom felt sorry for women, but this Rae Blackwood stirred a bit of pity in him. It might have been because he had never seen someone so thin or more likely because of guilt by association—Beauty Child felt sorry for Rae Blackwood, so he found himself feeling the same way. Additionally, since Beauty Child's heart was entirely focused on Rae Blackwood, there was a chance she might get distracted in battle, if indeed they were headed toward an actual battlefield with fierce fighting. He would be better off protecting Rae Blackwood themselves, allowing Beauty Child to be fully focused on the combat.
The most important reason was that Rae Blackwood had saved his life; without her intervention, his head would have long been abandoned in that pharmaceutical factory.