The army, like marriage, is an institution, not a right.. the membership of which corresponds to specific qualities which enable its societal mission. Homosexuality is a debilitating impediment to both of them.
Homosexuality may have some statistic relevance as negative, but statistics do not apply to individuals. Depression, drugs, etc., does not necessarily apply to the individual, just as being of a low risk group does not necessarily mean you AREN'T a depressed druggy with a propensity for beating your partner. Individuals applying should be looked at as individuals, plain and simple.