It's both relevant and not silly. The argument here is that nature does not supply "right or wrong", that is a human construct. Humans are a product of nature (if you don't believe in the god argument), therefore nature in fact, does produce a standard of rights and wrongs through men. Man is one of natures creations. Natural rights are rights man has realized for himself, each one individually. These natural rights exist because as does nature and as part of nature, man exists. Men do not control other men through any divine right to rule. Each man is his own ruler. That was the entire point.
I think we conflict on the definition of natural. Mine is perhaps more constricted.
Natural
:
based on an inherent sense of right and wrong <natural justice>
2a :
being in accordance with or determined by nature b : having or constituting a classification based on features existing in nature
3a (1) : begotten as distinguished from adopted; also :
legitimate (2) : being a relation by actual consanguinity as distinguished from adoption <natural parents> b :
illegitimate <a natural child>
4: having an essential relation with someone or something : following from the nature of the one in question <his guilt is a natural deduction from the evidence>
5:
implanted or being as if implanted by nature : seemingly inborn <a natural talent for art>
6: of or relating to nature as an object of study and research
7: having a specified character by nature <a natural athlete>
8a :
occurring in conformity with the ordinary course of nature : not marvelous or supernatural <natural causes> b : formulated by human reason alone rather than revelation <natural religion> <natural rights> c : having a normal or usual character <events followed their natural course>
9: possessing or exhibiting the higher qualities (as kindliness and affection) of human nature <a noble
brother
ever most kind and natural Shakespeare>
10a : growing without human care; also : not cultivated <natural prairie unbroken by the plow> b : existing in or produced by nature : not artificial <natural turf> <natural curiosities> c : relating to or being natural food
11a : being in a state of nature without spiritual enlightenment : unregenerate <natural man> b : living in or as if in a state of nature untouched by the influences of civilization and society
12a : having a physical or real existence as contrasted with one that is spiritual, intellectual, or fictitious <a corporation is a legal but not a natural person> b : of, relating to, or operating in the physical as opposed to the spiritual world <natural laws describe phenomena of the physical universe>
13a : closely resembling an original : true to nature b : marked by easy simplicity and freedom from artificiality, affectation, or constraint c : having a form or appearance found in nature
14a : having neither flats nor sharps <the natural scale of C major> b : being neither sharp nor flat c : having the pitch modified by the natural sign
15: of an off-white or beige color
Natural - Definition and More from the Free Merriam-Webster Dictionary
How is your strict" definition of natural and what were the founders talking about?