Because in fact, studies done on the emotional adjustment of children who are donor conceived, show that they have outcomes comparable to children who are not donor conceived......although they sometimes score more highly on measures of empathy and adjustment if they are aware of their origins (as do children of single women, lesbian and gay couples). I have a couple of books on donor conception, but an article I could lay my hands on quickly was an article published by the European Society for Human Reproduction and Embryology (5 July 2008) titled "Families with children without a genetic or gestational link to their parents are functioning well". I think the title gives you the idea of their findings.
There's a fabulous Oscar Wilde quote that goes:
"The old believe everything; the middle aged suspect everything, the young know everything
And it sounds like your relative is one of those....and as other posters have said, being involved in a dogmatic religion doesn't help that....it only makes it worse. I was raised Catholic and some of my family are remarkably blinkered. Perhaps at a family gatherings you could wear a t-shirt with some of these quotes instead? :
"Every mind was made for growth, for knowledge, and its nature is sinned against when it is doomed to ignorance"
Or how about:
The highest form of ignorance is to reject something you know nothing about.
Or my fave
You can swim all day in the Sea of Knowledge and still come out completely dry. Most people do