You can try strawman arguments like "they are not equally qualified" or "reverse sexism" or "they are doing it to themselves by not negotiating", but a cursory look at any reproducible social sciences review disproves those (laziness to not use google or google scholar is a tiresome excuse).
"equally qualified" is not an objective, measurable quantity, which is the whole cause of the issue... If dev productivity could be unambiguously measured and ranked, the issue of late promotions,etc would never have been raised.
These are fuzzy metrics, and what you consider poor\unfiar treatment, I may consider fair (and vice versa)..
The parent comment to yours was poorly worded and snarky, so you have a right to be upset. But still, I think your reasoning is flawed. People are generally promoted by their competence and their negotiating/office politics skills, and you can't claim that those are the same across all genders. Why would women, who are fundamentally different than men, have the exact same competence and negotiating abilities as men? There's no reason the two genders should be equal.
If you really have two equally skilled engineers, one male, one female, and only the male is promoted, that's sexism. But two engineers are never the same, so you can't make that argument.
You aren't allowed to reference social science studies because their aren't enough conservatives to make those fields "fair".
But say I'm doing a project in Java and they are about equal, I keep giving Al the meaty work then use it justify a promotion, which I can't justify for Marcy. It's not that she's that much worse, I just never gave her the chance to prove it (blah blah peter principle, perform at next level, etc...). That just might be a bit sexist.
Have you really never worked on a project where the golden boy was the face of everything and everyone else was ignored?