I would simply make the argument that women in the US Military did NOT serve in a front line capacity during the Cold War time period, which is when this game is set. There is no need to go off on tangents that will likely derail the thread with political correctness issues.
However, keep in mind that XCOM is a multinational organization. Other countries, such as the Soviets and Israel, have no such issues with using women a combat troops.
Therefore, I would argue that having female combat troops is an acceptable factor in this game. If you don't like it, you are free to selectively dismiss troops that do not meet your "physical standards", whether it be action points, strength, or gender. Multinational organizations generally are not subject to any sort of discrimination legislation either.
As a former Army tank gunner during the first Gulf war, I never served with women either. However, I was glad they were around working in the REMF areas like supply. It made evenings at the enlisted clubs a lot more interesting!