There's more evidence that homosexuality is socially caused rather than genetically (i.e., homosexuals do not pass on their genes, yet after countless generations there certainly are many about today). Of course, nothing is solid and it'll be many years before we understand homosexuality completely. Maybe it could be either, or both.
It is unfair to the children to be brought up into an unnatural environment. You might consider that everything will be normal for the child but they will have to be taught about homosexual relationships at a much younger age. What happens when the teacher at school gets the kids to make some paintings and tells them to take them home to their mummies? What's the kid going to think? Where is my mummy? why do all the other children have a mother and a father? Why do I have two dads? All this will result in much confusion to the child. Children should not be concerned with issues like this at this age, they have far more pressing work to do in developing.
As for where I get this supposedly random feeling as to why a stable family with a mother and father is a better environment for a child. Well lets put it this way: My mother was a teacher for > 20 years, as was my father. My mother was in primary schools and my father at a secondary where the kids from the primary would normally go. Between them they have seen hundreds of children grow from a young age to young adulthood. Naturally over the years we have spoken in length about the children and it is without doubt that children with single parents/family issues/unstable homes have the most trouble at school when it comes to working and behavioural issues. Children with stable family lives were usually more stable themselves.
There is absolutely no doubt that having two natural parents is better for a child. It is the natural method of procreation and social development. A child needs to have constant access to adults of both sexes in order for normal social development.
As for expelling all "abusive" children from schools... well that's a little absurd. Look at the above examples of children laughing at others because of large noses/ginger hair/etc. This is the way children are, they have not developed enough to be aware of the importance of accepting others for who they are not what they look like, etc. It's a dog-eat-dog world for children where they are constantly seeking to find their rank in the pecking order and define who they are. School is highly stressful and I would feel guilty condemning my child to years of torment if I were a gay parent.
I know there's countless examples of "normal" parents abusing children, but of course we never hear of all the examples where a family has worked out great for a child. In this age where we seem to becoming more distanced from the roots of what is a decent upbringing (e.g. MTV bringing up children, advertising aimed at kids, magazines for 12year old girls with tips on how to look more attractive to the opposite sex, etc etc) it is important that we try as hard as possible to maintain stable, natural families as much as possible.
There will always be too many children looking for foster homes-hell, one child is too many. I believe it would be more appropriate to focus on making child fostering more common and popular as well as finding and solving the causes of all the "unwanted" children (obviously parental death can't be avoided).
Children are losing their innocence too young these days. Having an actual emotional childhood seem to be becoming a thing of the past. Look at how young children are drinking/smoking/joining gangs/having children (some at 12)/shooting each other. They are treated to the realities of life at a far too young age where they simply do not have the maturity to handle these situations. The longer you can maintain a child's "innocence", the longer you can develop the many life skills they require. There is a point in a child's life where the parent no longer is their idol and instead it becomes their peers. At this stage there is much less that a parent can achieve with the child as their basic character will have reached a set irreversible stage of maturity here. Exposing a child to the true realities of life at a younger age is detrimental and will likely reduce this threshold age. A lower threshold age more often results in behavioural and social problems for the child.
Before I get all of the accusations of my being homophobic, let me make it quite clear that this is certainly not the case. I am very accepting, but I do not believe homosexuals should be in a position where they can raise a child.
My 2c.