We would like you to assess the QUALITY of each of the following argument (discussing Gay Marriage) and determine if the argument is Valid or Invalid. A valid argument is clearly interpretable and either expresses an argument, or a premise or a conclusion that can be used in an argument for the topic of gay marriage. An invalid argument is a phrase that cannot be interpreted as an argument or not on the topic of gay marriage.

a brother-sister marriage is not an extreme argument as the reasons you use should apply to those kind of marriages too if you wish to talk about it in terms of "equal protection".
Valid

I think few people would disagree that our society is already in just about as much of a conflict as it could be about this issue.
Invalid

Possibly, but changing marriage to allow such between couples of the same sex is going against the custom and usage of societies throughout the ages.

Valid