The Purple Heart is a military decoration of venerable age in our still-young republic. It signifies that the wearer has been wounded in the service of his country.
Imagine, if you will, that you are a soldier who has received this decoration, and you are proud to wear it.
One day, a judge decides that it's unfairly discriminatory to award this medal only to those who were actually wounded, and decrees that it must henceforth be distributed to every person who has ever served in a branch of the armed forces, even to those who were discharged dishonorably.
Might you not feel that the distinction awarded to you for your sacrifice was now devalued?
Now imagine that the people react to this judicial decision by formally reconfirming the Purple Heart in its traditional purpose, not once but twice. On both occasions, judges declare this expression of the will of the people unconstitutional.
The next time somebody asks you "How could gay marriage possibly harm heterosexual marriage?" it might help to ask them if they've heard of the Purple Heart.