In 1526 the Emperor called a Diet to meet at Spires in which favorable action was taken with respect to the evangelical cause, for religous liberty was granted to all until a council should re-establish unity. How mild, how lenient did Charles V show himself now! The friends of the Reformation rejoiced, the Catholics were chagrined.
Three years later the tables were turned: another Diet was to meet at Spires. Here the action of the former Diet was reversed and the Emperor demanded unconditional submission to the papal yoke. The princes were divided; six of them, together with a large number of German cities, declared that in matters concerning the glory of God and the salvation of souls their consciences required them to reverence God above all, and that it was not possible for them to yield to the Emperor’s demands. Because of this protest they and their followers were called Protestants.
By that definition I would gladly claim the designation Protestant. Unfortunately, the name is not so clearly recognized anymore. Sort of like the “Christians” you often meet.