The first is, as we have already seen with the expansion of the roles of women, steady downward pressure on military qualifications " reductions in strength and endurance requirements in order to get numbers up. The second is the risk of harm to female personnel: he people we are likely to meet on the next battlefield are people who use rape and sexual abuse as actual tools of politics. In Iranian prisons, rape is a frequent practice. Women are raped before they are executed. In Iran, in Pakistan, in Afghanistan rape is a conscious tool of subjugation and it is something women will be exposed to. In the name of equal opportunity they will face unequal risk. And the third point, one I think we should give real thought to, is the stress on military families. So these are some of the reasons why women shouldn't be allowed in combat. Not in direct combat.
On your first point, there is no need for the military qualifications to go down. If a woman feels as though she has a right to be on combat alongside her male soldiers, then she should have to work and put as much effort as they.
On your second point, rape doesn't happen only to women. Have you heard of rape within male prisons? Rape should not be only relevant to women because in the real world, it isn't. Besides, rape and sexual harassment does happen BETWEEN male and female American soldiers, so woman could possibly be exposed to any sexual mistreatment anyhow.
On your third point, the woman's family would only worry more if they had the same sexist viewpoint I am arguing. If a woman was treated as an equal fighter alongside a man, what is there more to worry about?