Leviticus 15:16-18
16'Now if a man has a seminal emission, he shall bathe all his body in water and be unclean until evening. 17'As for any garment or any leather on which there is seminal emission, it shall be washed with water and be unclean until evening. 18'If a man lies with a woman so that there is a seminal emission, they shall both bathe in water and be unclean until evening. NAS
I think the above should answer your question. Since God does not require a sin sacrifice for a seminal emission then how can God view this as sin?