^^ I am curious of this as well.
I am not going to say anything else about the situation as it really isn't my business to delve into your personal life. But I am curious as to what the tickle spot is/where it is.
I am guessing by flank you mean the area where the hair grows the opposite direction [it grows sort of up] between their stomach and hip? If so then I am surprised your mare kicks out because of that being touched. My gelding is trained that when I put pressure on that spot he is to move over. That is what I have done with every horse I have worked with. In that case, me being an experienced horse person unlike your DH, I still would have done the same thing he had done.