I'm new to these on line discussion things, but this is how i see things. Marriage is these days about a consensual relationship being aknowleded by the State. People can choose to have no religious input in their marriage service. Surely then you ARE saying that gays are inferior as they are not permitted/entitled to have legal proof of their relationship.
This is the true reason that children are not allowed to marry in this country. They are deemed not to be ready to make such a significant decision. In other countries and in the past children were married off, and it certainly was not for thier protection!
Of course when it comes to a marriage sanctified by a church, then it should be down to each church to decide if the practice fits the views that it holds.
As regards your stance on abstinence education. Yes this i agree is a good thing, but not if it is the sole education given. People should be given the information they need to make an informed decision. This cannot be done if only one option is presented.
And as far as contraception goes: Yes it most certainly should be made available to as many people as can possibly access it. Did you know that in developing countries the current most widely used form of contraception is anal sex. This is the most risky in terms of STD infection, and could be largely eliminated if those people had access to and were educated that it is ok to use condoms. This is one of the most untalked about causes of the huge epidemic of HIV/AIDs.
May i also add, that regarding your comment on the problems of single parents, many single parents i know/ know of had teenage pregnancies, largely preventable by contraception. The rest are from divorces which provees that marriages between heterosexuals are imperfect by far. Gay marriage would have little impact on the amount of single parent families.