Ah I get you now.
We are part of nature. We act according to our nature...
We aren't "going against" nature.
we attempt to destroy and circumvent nature all the time. birth control is not natural. abusing and sodomizing a child is not natural. raping the planet for the sake of making money off of some bobble is not natural. everybody and their children on drugs is not natural. obesity is not natural. slavery is not natural. war is not natural. having sex with battery operated machinery is not natural. and the list goes on...
Nope. Sin is a religious concept.
And it's not a "law". (Neither legal nor physical).
yep. sin is anything that results in sickness, suffering, and death. greed, lust, gluttony, sloth, wrath, envy, and pride are not concepts, they are very real things that make us all suffer, because according to law, the results of these things are destruction.