But nowadays men have even a stunt of pretending that children and idiots alone know best.

This is a pretty piece of sophistry, and criminal cowardice, trying to dodge the life-responsibility which no man or woman can dodge without disaster.
The only thing is to be direct.

If a child has to swallow castor-oil, then say: "Child, you've got to swallow this castor-oil.

It is necessary for your inside.

I say so because it is true.