What is the meaning of Harrison and the ballerina being shot down by Diana Moon Glampers, the Handicapper General?

The meaning of Diana Moon Glampers' cold-blooded action is that insubordination will not be tolerated. Everyone is required to be equal, whether it is desired or not, and all infractions will be severely punished. The cold-blooded murder of Harrison and the ballerina represents the dangers of allowing a government to force equality on an unsuspecting and defenseless populace.
In Harrison Bergeron's world, no one is allowed to be "smarter than anybody else" or "better-looking than anybody else." Thus, Harrison's attempt to exert his individuality is summarily punished. As an enemy of the state, Harrison is in a dangerous position. He rejects the wearing of handicaps that are a requirement for someone as good-looking and physically gifted as he is. In the story, he is described as a "genius and an athlete."
Towards the end of the story, Harrison relinquishes the thick glasses, massive earphones, and the scrap metal he has always been required to wear. As he dances and swirls about the floor with the ballerina, Harrison revels in his freedom. Alas, his happiness is short-lived. Both Harrison and his dancing partner are fatally shot by Diana Moon Glampers, the Handicapper-General. Diana's brutal action represents the danger of allowing a government to enforce its own vision of equality on its defenseless citizens.