I would say "explain how it differs from majority", not "convince that it is not normal", and I meant not the whole everyday life, but a particular aspect of it. Because other people will eventually persuade of it anyway, and it will hurt. *Maybe* this is what this man was talking about.
I agree that it is important to talk about families, and how families are different. But you know what? I'm pretty sure that most families "differ from the majority" in some way or another. Here in the US, how many families are living with a parent who is or was deployed in Iraq or Afghanistan? How many kids live with mom Monday-Friday, and with dad and step mom on weekends? How many families have grandma living in the converted garage? How many kids have a parent in prison, or a parent who is undocumented, or a parent who is away on business more than s/he is home? How many families are multi-racial, or multi-ethnic, or have parents or grandparents who believe in different religions? How many kids have an autistic brother, or a mom in a wheelchair, or a dad who is in denial about the post-traumatic stress he suffered during his military service? And there are a lot of kids who lost a parent in one of those wars. How many kids were adopted, or are living in foster care, or are living with step-siblings?
I'm a middle aged single adoptive mom of a child who is a different race from me. We are certainly different from the majority of families. I tell my daughter that all families are different. I also (try) to offer her the tools that she needs to deal with the misconceptions of others. When she was in pre-school, a child told her that kids only get adopted when their "real parents" die. She came home and asked me about that. I told her that a lot of people don't know much about adoption, and that she knows more than most kids, and she even knows more than many grown ups. I told her that she could help educate people about adoption if she wanted to, and we talked about some of the specific things she could say.
A couple of months ago, on the bus ride home from school, another 6 year old told my daughter that everyone has to have a mommy and a daddy. The little boy went on to say that President Obama said it was the law. The second statement made it easy to laugh. I explained that everyone has a "biological" mommy and daddy, but that all families were different. I went on, with the help of a neighbor, to tell my daughter about Obama's childhood, and how his biological dad left the country, and how he was raised by his mom and his stepdad, and then by his grandparents.
Kids who grow up surrounded by love and nurturing are lucky kids. I don't talk about the little 6 year old whose dad sleeps drunk on the playground bench for so many hours while my little one plays with her little friend. This spring/summer, perhaps my little one will notice that there is a loose community of parents who look after this little girl, because her biological father, (who was granted custody on weekends) does not seem capable of taking care of his daughter. This will be a big, hard discussion.
My sweet little girl believes that all parents take care of their kids. It will be really earth-shattering for her to learn that this is not true. When she looks at the moms and dads, and the two dad families, and the two mom families, and the single mom families, and the families with nannies who spend more time with the kids than the parents, she sees kids who are loved and protected. At a certain point, she will lose her innocence, and learn that not all kids are protected by those whose responsibility it is to keep them safe.
That will be really shocking for her.
And unlike the two dad/two mom families that you are so concerned about, it is a real social problem.