Natural  Law, this import from ancient Greek philosophy is at the root of RC moral theological problems.  It assumes that sex is mainly about making children and that there is a natural dominance of males.  Natural Law theory, for that is only what it is, infects and damages much about Catholicism.  
It is one reason why "Catholic Church officials still dither and wring their hands over whether long partnered, now even married, same-sex couples are living in sin, a matter long settled in the minds of most American Catholics. "  
The other reason is that the quoted argument deals in social acceptance instead of theological discourse.  The writers do not propose any theological basis for their position, only this social acceptance.  For a real discussion rather than just a rallying of supporters, the writers need to come back with a theological alternative to Natural Law as a basis for the formation of conscience.  The writers are not offering any theological challenge to the status quo.