No, it should not. That's just ridiculous. You don't fix unequality by maintaining it just because that's what you're always known. You want to keep the privileges you have now while denying improving the situation of others, because you think losing your unfair advantage over others becomes unfair to you, that's nonsense.
Hiring 50/50 is not discriminating against you just because you were at 70 before. You don't get to decide that half the female population of the planet shouldn't be allowed to work - because that's what your 70/30 is, if the 70 is most of the male population (let's imagine a >90% employment rate), then the 30 is around half of the female population, you're saying the other half will never be allowed to work. You're assuming they can keep being SAHM or whatever else.
The thing is that the 70% of workers being men shouldn't mean there are less men if it becomes 50%. Men aren't losing their jobs. It means there are more workers, including the same number of men, and more women. This isn't supposed to be a zero sum game when population grows.