I think giving people the freedom to choose and compete for the jobs of their choice is not only just, it is smart. What business will do better: one who will only hire people who are tall/brown eyed/born in Texas/male/white/whatever...or those who will hire the most qualified candidate regardless of those other attributes?
If women can do the job as well or better, I say, let them.
But the reality is that the issue of women in combat roles is no different than what we've seen with women in many other "traditionally male" roles. You probably couldn't find a single law enforcement agency, fire department, etc. that hasn't instituting "gender norms" that hold women to lower standards than men for identical roles.