A female Army Ranger candidate crosses the Yellow River on a rope bridge at Camp James E. Rudder on Eglin Air Force Base in Florida. (Nick Tomecek/Associated Press)

SECRETARY OF the Navy Ray Mabus has made clear that nothing is likely to change his intention not to seek exemptions in the opening up of military jobs to women. He doubled down in the face of a Marine Corps study raising doubts about the ability of women to serve in combat units. Mr. Mabus is right to argue that the emphasis should be on standards that ensure excellence in the military, and on whether individuals — no matter their gender — can meet those standards. But by cavalierly dismissing, even impugning, the concerns of Marine officials, he inadvertently helps those who say political correctness is driving the push for full integration of the armed forces.

The Pentagon announced in 2013 the lifting of a ban on women serving in ground-combat roles but gave the services time to request exceptions. With the deadline for those requests approaching at the end of the month, it appears likely the Army, Navy and Air Force will not seek exceptions that close off jobs, including those in demanding commando units. But Marine Corps leaders have expressed concerns about allowing women to serve in infantry roles and, according to the Associated Press, are expected to ask that women not be allowed to compete for several front-line combat jobs. That not only would seem to put them at odds with the other services but with Mr. Mabus, who, as Navy secretary, is in charge of the Marines.

Heating up the dispute is a year-long study by the Marine Corps on gender integration that concluded that male-only units performed better overall than gender-integrated units. A summary of the report showed that male-only infantry units shot more accurately and could carry more weight, and that women had higher injury rates than men. Mr. Mabus took issue with the study, saying the fact it “started out with a fairly large component of the men thinking this is not a good idea, and women will not be able to do this” could have affected the results.

There may well be, as Mr. Mabus argued, problems with the report’s methodology and its reliance on averages. But attacking the motives of Marine officials was out of line, opening the secretary up to charges that his decisions are being shaped by politics. That could unnecessarily muddy the waters on the critical issues posed by the changing role of women in the military.

Defense Secretary Ashton B. Carter has until Jan. 1 to decide what, if any, exceptions to grant. It’s important he listens to all sides and evaluates all the data and that he makes clear that the judgments made are not based on politics or emotion, but on the best interest of the armed forces and the country they defend.