When my children were small the early evening news never showed anything violent etc but now they do. I think it is sad that today's children lose their innocence at a young age - whether it be about wars, death, sex or whatever. I suspect that in many homes the tv is on all day and they see and hear all sorts of unsuitable things. Pop stars and so called 'celebrities' are their new role models from the age of 8 if not before.
I would never lie to a child but would be economical with the truth, and there is no harm in falling back on 'you'll understand when you're older' or ' It's a secret for big girls (or boys) ' as a last resort.
I've got another 'keen'... Ouch!