Spankings are not discipline "Spanking is a sex act" Jillian Keenan at The Slate

[pnwmom]

36. Actually, you are also incorrect about children not being stimulated during molestation.

It doesn't matter that a boy doesn't ejaculate; he can still have sexual feelings. One of the issues victims of child sexual abuse face is guilt because they DID respond to the abuse with sexual feelings to the abuse. But the feelings were an automatic physiological response. They didn't want those feelings any more than an adult who is being raped.

https://www.rainn.org/get-info/effects-of-sexual-assault/adult-survivors-of-childhood-sexual-abuse

Guilt, shame and blame

Survivors may feel guilt or shame because they made no direct attempt to stop the abuse or because they experienced physical pleasure

http://nospank.net/sexdngrs.htm

“When a child is hit on the buttocks... [t]his kind of violent touch can be sexualized in the child’s mind not only because of a real flow of blood into the genitalia, but also because of a longing for intimacy with the parent: if painful physical touch is the only fulfillment of that longing, then this can “feel good.” 
Shere Hite, sex researcher, sociopsychologist. The Hite Report on the Family (1995)