What are the views on the legalization of gay marriage?

The definition of marriage is always changing

Question: What are the views on the legalization of gay marriage?
Position1 of 4›: Gay marriage should be legalized
Argument1 of 4›: The definition of marriage is always changing

The definition of marriage is constantly shifting as societal attitudes change.

The argument

In the past, our definition and understanding of marriage included polygamy. Some societies that shudder at the idea of taking multiple spouses today once saw nothing wrong with it. The same applies to interracial marriage. At one time, interracial marriages were abhorrent and even illegal. Few hold that belief today. Our definition of marriage evolves and changes with public opinion. It makes sense that as attitudes to homosexuality change, so too should our definition of marriage.

Context

Marriage has never been a fixed concept. Allowing same-sex marriage is a natural evolution of the concept.

Premises

[P1]The definition of marriage has always changed, once including polygamy that many societies now reject. [P2] Interracial marriage was likewise once abhorrent and illegal but is widely accepted today. [P3] Our definition of marriage evolves with public opinion, and attitudes toward homosexuality have changed. [C] Therefore, because the definition of marriage is always changing, gay marriage should be legalized.

Counter-arguments

Our definition of marriage can only be expanded when public attitudes force it to expand. This is not happening everywhere. There are many countries where public attitudes remain obstinately opposed to gay marriage and same-sex couples. Until societal currents force the definition to expand, the existing definition of marriage between one man and one woman must prevail.

Rejecting the premises

[Rejecting P2] Public attitudes have not necessarily warmed to gay marriage.