1) “Marriage, the union of a man and a woman…” – Unless you live in one of America’s six states or the District of Columbia, or one of the several nations, that has legalized marriage equality. It’s about denying reality, folks.
2) “Marriage is more than what adults want for themselves, it’s also about the next generation.” – This pretends that marriage is what makes babies happen. Out-of-wedlock teen mothers bedevil this. Also, we know the “marriage is for procreation” line doesn’t hold water because we do not deny the elderly or the infertile a right to marry.
3) “Marriage provides children with the best chance of being raised by a mother and a father.” – Well, yes it would do if you only let straight people marry and then tie adoption rights to heterosexuals-only marriage, as has happened in some states.
4) “Children do best when raised by their married mom and dad.” — The implication of this non sequitur is that children need a mother and father in order to flourish. No peer reviewed, consensus-backed study has shown that the gender of a child’s parents matters, and there is a wealth of evidence to suggest that same-sex parents provide kids with just as nurturing an upbringing as their straight counterparts.
5) “Nobody is entitled to redefine marriage.” — Really, because we’ve been doing it for quite a while now. From contracting for land, to trading women for cattle, to allowing multiple partner marriages, and, yes, allowing same-sex marriage; marriage has been redefined countless times throughout the ages. Furthermore, we as a society do have the right to change what we consider a civil marriage, otherwise you wouldn’t be able to define away gay marriage rights, and therein also have a right to end the inequality same-sex couples face in tax laws, state level recognition and federal benefits, all of which are tied to marriage.