Suppose I am sincerely concerned and asked this question:
I should keep a pink unicorn in my back yard, but what if it poops in my garden?
The characteristic of this question is that the "second part" about pooping sounds like a possible situation that can happen with pink unicorns, but the "first part" is an imperative that cannot happen (or lack evidence) because there is no such thing as a pink unicorn.
What do you call the first part, second part and this type of question generally? Is there a specific terminology? Is it meaningful to answer this type of question or not? How do I approach it?
This type of question may appear as other forms that may look more genuine:
People should have absolute freedom, but what if they start doing nasty things to others? I should believe in God, but what if I am wrong?