The real issue here is that society is a group of people living together and amongst each other. It is how nations are formed.
The basic building block of society is the family. It takes a man and a woman to make a child (forget for now the stupid sperm and egg donor crap), and it takes a family to raise a child (not a village!).
Homos cannot create families.
Allow homos to marry and you break down marriage.
Break down marriage and you break down families.
Break down families and you break down society.
Break down society and you destroy a nation.