What? What in hell does the selective service, which you register for at 18, have to do with voting? Unless I am a crazy person, they have nothing to do with each other.
Members of congress declare war and people vote for members of congress. Logically all voters, men and women, should have to register for selective service because they are taking part in a choice which affects the possible declaration of war, which can lead to a draft. Voting without having to also register for the draft means taking part in a decision making process that can only risk the lives of others. This should ave been taken into consideration with the implementation of the 19th amendment. If it is illegal to discriminate against voters based on sex, then it should also be illegal to discriminate against who should be required to defend that vote based on sex.