Many of the most talented or hardest working engineers might rationally be opposed to equal pay measures.
Not clear why a talented and hard working person of one gender would be opposed that a similar person of another gender get same pay?
It did not refer to people making unequal contributions.
Because there might not be an even distribution of people with certain skills. For instance, some point to the disproportionately large number of Asians in higher paying roles, and demand a form of equalization.
The issue is not that people don't believe in equality, it's that people don't have the same view of what is equal. In particular, some view equality in terms of equality of outcomes while others view it in terms of equality of opportunity.