The more I think about, the more I think the rank and file of the jayhawkers were western men. The frontier always attracted the type that fell into lawlessness when the constraint of law enforcement was absent, and during the Border War was there not only the absence of law enforcement, but there was active encouragment of the lawlessness, for example the demagoguery of Lane.
And here are a couple of quotes by Charles Robinson, from his The Kansas Conflict, and the chapter entitled Lane and the Jayhawkers, that illlustrate this New Englander was no supporter of the jayhawlers:
"When January, 1863, arrived, the first State Governor gladly delivered up the executive chair to his successor, Governor Thomas Carney. Enough had been seen and experienced of the management of the war in the West, permitting the most brutal and inhuman outrages, all to gratify personal greed, malice, or ambition, to disgust any person not entirely given over to subsisting upon human misery."
"Quantrell was more considerate than Lane had been, as he told one of his prisoners, taken at the Eldridge House, that he should spare the women from outrage, which Lane in his raids in Missouri did not do. He also said, as Robinson, while Governor, did what he could to preserve peace on the border, he should not molest him or his property. Of this intention Robinson had no knowledge, but both his person and property were spared, although the raiders were within a short distance of him, and in full view, and could have destroyed him and his property without trouble. Had the raid not been for retaliation for similar raids in Missouri, there is no reason why Robinson's property should not have shared the fate of Lane's, nor why he should not have been killed as were others when completely in the power of the raiders."