Ok, lets look at these reasons against gay marriages.
Claim #1 - Marriage is an institution designed to foster the love between two people. Gay people can love each other just as straight people can. Ergo, marriage should be open to gay people:
(Their answer is...)
The second statement is true, and the third follows logically from it. Because the first statement is false, however, this line of reasoning makes no sense. Marriage is a complex institution. Fostering the emotional gratification of two adults is only one of its functions — and not the most important one from a cross-cultural or historical perspective. (It might not be accidental that this exclusive focus on emotional gratification coincides with a high divorce rate.) The question is not whether gay people should have relationships. The only question is whether this should be done in the specific context of marriage.
Once again we see the answer involves "...is only one of its functions - and not the most important one....", but no real explanation of what the other functions are or what is most important.
"Marriage is an institution designed to foster the love between two people." seems a perfectly valid definition of marriage to me. And it seems that this definition would fit what many people consider most important in a marriage.
Claim #2 - Not all straight couples have children, but no one argues that their marriages are unacceptable:
Their answer?
Actually, that is an oversimplification. Some religious traditions, for instance, have given childless couples the possibility of divorce or annulment. Besides, marriage can function in additional ways (one of them being companionship) and can express additional ideals (the most obvious one being love). Consequently, these traditions do not insist that childless couples separate. Instead, they maintain what they consider the one distinctive ideal of marriage without punishing those who fail to attain it. The latter are exceptions. This institution has always been intended primarily, however, to serve the needs of children. It provides an ideal scenario for parents and children. Not every individual or individual couple lives up to the ideal, of course, but the ideal remains effective nonetheless — except, of course, in societies that are breaking up.
It is not an oversimplification. It is an answer to the claim that children are the main point of marriage. And it is a valid point. And there was a time, not so long ago, that a single mother was either a widow or a social outcast. People married because they got pregnant. And stayed married because of the children. Few, if any psychologists would agree that either of these are ways to a good relationship.
Also, notice the veiled threat with "but the ideal remains effective nonetheless — except, of course, in societies that are breaking up.". The attempt to place a dire warning on the consequences of gay marriage. But sadly, straights have already screwed up marriage enough for both groups.
Claim #3: Some gay couples do have children and therefore need marriage to provide the appropriate context:
Their answer?
This claim reverses the other one by accepting the premise that marriage is indeed the ideal context for children. The problem is that gay marriage would provide that context in name only. Our point here is not that gay couples are less able to love their children than other couples; they are neither more nor less able to do that. Our point here is not, moreover, that gay couples would teach their children to be gay; the mere fact of being gay, from our point of view, is not problematic in any case. The point is that children require more than love from their parents, whether gay or straight. One thing that they surely require is at least one parent of each sex. (We say "at least" one, because an extended family — with aunts, uncles, and grandparents — is much closer to the ideal than the isolated nuclear family.) That is because the sexes are not interchangeable. (there was considerably more)
The fact is that a huge number of children are being raised in families without two parents. If children require two parents of different genders (so much so that gay marriage is not allowed because of this) then parents with children should not be allowed to divorce. The claim that two parents of different genders is the idea ignores the multitude of other factors that parenting requires.
Claim 4: Marriage and the family are always changing anyway, so why not allow this change?
Well, yes, of course, institutions change. Whether they always change in beneficial ways is another matter entirely. Unless we adopt the mentality promoted by countless ads and commercials — according to these, every product is "new and improved" — we must at least imagine the possibility that some changes might be for the worse. There is no logical connection, in short, between either "new" and "improved" or "changed" and "better." Marriage has changed for the worse in some (though not all) ways, we suggest, over the past forty years. Not by gay people, of course, but by straight people.
And whether institutions change in all ways is yet another matter. Some features of marriage have not changed; these are universal and therefore, presumably, both necessary and beneficial. Marriage has always been a matter of communal importance, for instance, one that serves more than individual needs. These things are so pervasive and so enduring that they might as well be due to nature itself. We play with them at our peril.
We have already played with them and the world did not end. If anything, gay marriage would be a way to reverse the trends towards single parenthood.
Claim 6: Children would be no worse off with happily married gay parents than they are with unhappily married straight ones:
This comparison is false, because it involves the best of one scenario with the worst of another. A legitimate comparison would compare either the best of both or the worst of both. Once again, we suggest that the best of marriage (providing at least one parent or other adult of each sex) is better for children than the best of gay marriage (which provides two parents of the same sex and none of the other).
This claim is completely valid. The comparison of an unhappy straight marriage to a happy gay marriage is very much the valid comparison.
The reason is quite simple. If gays cannot marry or adopt children, then they will stay in bad marriages to stay with their children or to be able to raise children. This is especially true of lesbians. The maternal instincts are very strong. But our society has, very often, made them choose between their children or their own life of love.
Claim 6: Children would be no worse off with happily married gay parents than they are with unhappily married straight ones:
This comparison is false, because it involves the best of one scenario with the worst of another. A legitimate comparison would compare either the best of both or the worst of both. Once again, we suggest that the best of marriage (providing at least one parent or other adult of each sex) is better for children than the best of gay marriage (which provides two parents of the same sex and none of the other).
Now they are reaching and spreading bullshit.
The population issues are real. They may not cause huge issues today, but they will one day. To ignore them is stupid.
As for the immigration issues, that is total bullshit. Look at the cultural differences of the USA and Mexico. Does Mexico see the divorce as socially acceptable? Do they see homosexuality as equal? No. But they will immigrate here in a heartbeat.
Claims 8 & 9 were stupid to begin with.
The rest seem to be selective claims that can be dismissed without applying any real effort.
I'll read it again in a while, but for now this should suffice.