From the link
"The shudras are the only section of society allowed to accept another’s employment"
As I am an employee now, as are many of my brahmin friends, are we shudras now? If I start teaching the holy books, do I become a brahmin?
What the hell does duties according to ones nature mean? Who decides ones "nature"? A single person can be an employee, warrior, priest or businessman. What is the point of forcing people into categories?
What does it mean to perform your caste duties and nothing else, even if I am better at something else? How does that jive with "duties according to ines nature". If I am an employee, can't I have a side business.
Why is there so much worry about marriage across caste lines? Why fret about varna sankara? It is obvious that you get your caste by birth, not by your acts. If you perform your caste duties without asking questions you get an upgrade to a higher caste in the next birth. Ultimately, becoming a brahman. You can cross check with any guru in a temple you like, instead of arguing with me.
Examples of shudras becoming brahmins are pre-bhagavata gita. After the gita, such a caste transition is only possible via the cycle of death and rebirth.