I wonder if the writer of the letter referring to nudity is really living in the 21st century? It sounds like the kind of letter that would be written in Victorian Times.

I do not know the ages of his children. Will they not be allowed to go to art galleries where nude pictures or naked bronze figures are exhibited? Will they be excluded from the class when the anatomy of the human body and sex education is taught? 

The pictures you showed were no more revealing than what can be seen at any swimming pool.

 I don't think you have anything to apologise for, I am sure most of your readers thought they were fun.

Margaret.