But Robert's uncompromising and obviously uncowed attitude called their bluff. And it appears that it was bluff. Probably the imprisonment of bankrupt Robert Burrowes would have been dysfunctional in these regards. The purpose of imprisonment is usually stated as being retribution, rehabilitation and deterrence. Retribution in this case would seem very petty and mean minded.
Deterrence is the only possible explanation for imprisoning a conscientious redirector of war taxes.
But even this is extremely problematic. Robert had demonstrated that he would not be deterred. This leaves general deterrence - preventing others from taking similar steps. Very few people sit bolt upright in the middle of the night and realise that they have to stop paying for the military. Those who take this step have generally thought about it for a long time, they are not the sort who will be deterred.