An Analogy For Penal Atonement

I’d like to share an experience I had this evening. A mother was tending to her crying baby, presumably related to the pain of teething. While trying to comfort the baby, the mother said,

Aw, I wish I could take the pain of teething for you…

I feel confident in asserting that the majority of individuals would both approve of the mother’s loving intentions, and encourage her to take the pain if she had the means. So why is it that such a disproportionate subset of people  object when Christians preach a God both willing and able to take the pain of sin for us?