Anything powerful should be handled carefully. If we don't handle them properly it would create havoc and disaster. For instance, if we get a flammable substance we wouldn't put it anywhere carelessly. We would put it in a safe place unlike a rock which can be put anywhere without problem. Men are of neutral energy like a rock and doesn't have special needs and care.

But, women are of high energy and they should be handled with proper care and attention. If we put them in the position of a diksha guru, the kind of atmosphere it creates is difficult for most of the men to handle. 

For instance, a man at workplace has to just do the work mechanically under a male boss and if it's a female boss he has to handle it differently. Men get confused if they are put under a female boss who has different needs. 

References from Bhakti Vidyapurna Swami Maharaj class on she can't become a guru.

Prabhupada: Yes. Three kinds of happinesses, bhoga, tyaga, and bhakti, seva. Bhoga tyaga seva. The karmis, they are after bhoga, sense enjoyment. And the jnanis, they are after another side of negation of sense enjoyment. When one is fed up with sense enjoyment... Just like in your country, the young boys, they are practically fed up with the way of sense enjoyment as their fathers and grandfathers had done. So in the name of tyaga, renunciation, they have taken another kind of sense enjoyment -- intoxication, unrestricted sex. So this is also another sense enjoyment. Bhoga and tyaga. Real enjoyment is devotion. There is a very practical example. Just like if you get all of a sudden a certain amount of money, say, one hundred rupees note lying on the street, if you get... Or lying here. So if you take it, your conscience will beat, because that does not belong to you. You have picked up. You'll always think, "Oh, I am taking somebody's money. Whose money it was? I'm doing some sinful." In this way, your mind will disturb. So that is the taking. And similarly, if you don't take, if you leave it there, then you'll also be disturbed. You'll think, "Somebody has left this money here. So I did not collect it. Somebody will collect it, and he'll take it away. This is not nice." The best thing is that you pick it up and, if you deliver to the person who has lost the money or who has left that money. Three things. The one thing is bhoga, if you take yourself. And if you don't take, that is tyaga. And if you pick it up and deliver to the right person, that is devotion.

>>> Ref. VedaBase => The Nectar of Devotion -- Calcutta, January 29, 1973