Since his religion doesn’t recognize any other Christians, that is a valid and important question [Holy See status].
Do Catholics really recognise other non-Catholic Churches as legitimate.
There are pentacostals who dont recognise other non-pentacostals as Christian groups.
Infact there are many Christian groups who consider their Church as real and others not which does not belong to their group.
This is a silly question and Mitt does not have to answer it.
How is that any different than what you say about his religion? Hypocrite.