“Hey, Im glad we got into WWI but munitions should not have been shipped in passenger liners. Bad idea.”
Unfortunately because the British government subsidized a good deal of the construction of the Cunard and White Star fleets, there was an agreement in place that during wartime they could use those ships for the war effort, whether it be taking them out of passenger service and conscripting them as troop ships or to carry materials to aid the war effort in the course of their regular travels.
While this might have seemed like a good idea it created a gray area where these ships could possibly be considered legitimate military targets. Mixing both civilian and military functions in the same trip was terribly dangerous.
Titanic's sister ship, the Britannic, was conscripted into service as a hospital ship in 1915 and made five successful runs to the Middle East to evacuate casualties from the campaigns against the Ottoman Empire. During the first leg of her sixth trip to the war zone, Britannic was passing through the Kea Channel off Greece when she struck a mine laid by U-73 and sank. Two days later, another passenger liner-turned hospital ship, the HMHS Braemar Castle, struck another mine laid by this submarine and was severely damaged. Fortunately both ships were on their way to the war zone, so casualties were minimal.