Children are generally socialized through their parents. That includes politics and ideology. I think "milk" is as valid an argument as any. As for tactfulness, I don't know if it's specially effective. It might be. But some of the people who had the most impact on my thinking were neither tactful nor nice about it. But I suppose it depends on the kind of discussion and the type of person.
But being tactful and not getting into heated arguments would preserve one's own sanity. So there's that.
And milk is great btw.
Are you making milk great again?
Barf!