The military isn't really a good example at all.
Typical Governmental employment would fall under the existing Civil Rights Act.
But the military is far from a typical case.* They have greater latitude to discriminate as appropriate to the mission.
Another example would be handicap.* There are laws that prohibit discrimination based on handicap, but the military CLEARLY CAN discriminate based on handicap...
*
And on the second comment, we have no dispute.
However, enacting an ERA would arguably not even*apply to*the issue of military treatment regarding gender.
*
But side-stepping that, what's the real gap?*
What would the ERA cover that is currently not covered by the 14th amendment and its application to gender?

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“Labor is prior to, and independent of, capital. Capital is only the fruit of labor, and could never have existed if labor had not first existed. Labor is the superior of capital, and deserves much the higher consideration.”
~Abraham Lincoln