Taking the Last Bite, Should I?

Here's just a little lesson that's good to review with our children, before they find themselves faced with this situation.  I find that if I discuss with my children ahead of time (not in the moment), they are much more likely to listen and to ponder what has been said.
Proper Etiquette regarding taking the last piece or bite of something is simply; ask first.  Have you ever been “eyeing” the last piece of chocolate pie and wondering whether you should go for it or not.  Well, it’s OK if you do, but the polite thing is to ask if anyone else would like it, before you take it.  For instance, “If no one is going to eat this last piece of pie, I would love to have it,” or, “I would be willing to share.”  Most people, unless it’s your brother, are going to say, “No, you go ahead and enjoy it.”  People appreciate so much your willingness to ask before you take, that they usually allow you to have it, even though they might love it themselves.  This rule applies to everything, whether it’s the last piece of cake, the last piece of pizza, or the last piece of gum.  It’s amazing the payoffs that happen when we use proper etiquette.  Another consideration is asking for "seconds."  Remember, that when you’re in your own home, it is perfectly polite to ask if you may have "seconds."  However, when you are a guest in someone’s home, it is impolite to ask for "seconds"; wait until you’re offered "seconds," and then it’s perfectly OK. 
Now that my children understand this, are any of you willing to explain this to my husband?  Let me know if you have any suggestions for this problem.  I give up:)
Monica, a.k.a. Ms. Mary Manners