Could it be that Dale's tribe was at war with Kate's tribe? After the scuffle in the hospital, he had shown no signs of aggression towards Kate, and had taken an interest in making sure that her treatment was effective. That wasn't how enemies behaved: she knew from the Hearth's Warming pageant that the earth ponies of old would have happily stood by while the unicorns starved to death, even if in so doing they doomed themselves. The schism was too deeply seated for it to have been any other way, and if it hadn't been for the stroke of luck that brought the three tribes together, there might not have been a modern Equestria.