Complex sentence: Spee was the first person in his time who wrote and spoke strongly with arguments against torture in general, and why it is not a way of obtaining "truth" from someone undergoing painful questioning.
Split into simpler sentences: Spee was the first person in his time who wrote and spoke strongly with arguments against torture in general. He may be considered the first who ever gave good arguments why torture is not a way of obtaining "truth" from someone undergoing painful questioning.