"There comes a certain point where one must weigh the balance of morals and one's own neck," Ichabod says simply. He isn't going to abandon his principles, no, but if he can manage to gain Hal's trust somehow, perhaps there is a chance he can slip away. He will get but one chance to do this because he imagines that if he were caught, it would be a messy and bloody death in his future and not another escape plan.