What basic employment right are they denied that straight people are not? They are not asking to get equal treatment under the law, because they already have it.
You do understand that women in the military are given preferential treatment, right?
Well, for one, women were not generally allowed to vote 100 years ago in the US, and since you didnt specify country, I will point out Apartheid.
What's at issue is at what point one person's freedom must be elevated above another's.