The closest thing I can think of to this issue is having your child molested. Early in my LE career, I had to work child molesting cases. Now, everyone pretty much says, and really thinks, they would kill anyone who molested their kids. I know I feel the same way.
Yet, out of all of the child molesting cases I worked, I only saw it happen one time. And, that was a mother, who within a few minutes of finding out, took a butcher knife and tried as hard as she could to stab her daughter's attacker to death. And, then, three months later, she was living with him again.
I saw a lot of people get really mad, but I never saw anyone else actually do anything.
But, you ask anybody, me included, and we all say we would kill the bastard.
I sure miss the country I grew up in.