Gyomei Himejima, the Stone Pillar, is a very emotional being by nature. He possesses a very kind soul that often weeps for the innocents he couldn't save. As I've answered in the previous question, Gyomei is the strongest among the Pillars. This status is also thanks to his ability to feel every emotion strongly. He harnesses these emotions and uses them to fuel his breathing. So his crying is more like his strength rather than weakness.