Naivety is often equated with being young, but it can happen at any age and at different moments. It's actually not such a bad quality and carries - I think - an unjustly negative image.
I think naivety carries an unjustly negative image just as emotionality and many other human aspects do too, and this is one of my main problems with the world and something I've always been trying to advocate for as this is an important aspect of life even though many think the opposite.
Yes, I agree, I think it may be for the reason that naivety provokes some envy or longing from someone who lost his or hers (or thinks he did) and then can't stand the moment of a naive response or action.
Emotionality is a bit more difficult, for there is a wide range of emotions circulating and when people talk about themselves being "all rational and not emotional" they forget that there is not only anger, rage or sadness but also joy, humor, silliness etc. and that every human being on earth is having and deciding upon them, no matter what they tell otherwise.
One cannot and will not avoid emotions, but one can accept them as they arise and not make a big fuzz about them. Usually every emotion disappears after a while, cause, just imagine you'd laugh for a week or rage for a whole months (guess, one would drop dead even after some hours) :)))