Even in the 21st century we live in what is essentially a primitive tribal culture. Each person has their role, men to protect the tribe and gather provisions, women to maintain the living conditions and raise the children. Each of these roles is essential to survival of the tribe and anyone who looks as though they won't completely fulfill their role is a perceived liability to the tribe.
Men in women's clothing is perceived as a rejection of these essential gender roles and I believe that, deep down, it is still perceived by the observer as a threat to tribal survival. A man in a dress isn't prepared to fight and therefore won't "pull his weight" for the tribe. This threat doesn't bear close examination in modern context, but emotionally it is not examined and a negative feeling results that is expressed in various ways, almost all negative.
Modern women have been able to go beyond their gender roles in some ways, but they are still somewhat trapped. They still feel pressured to "stay home with the children" or to "be good homemakers" despite their forays into the masculine world of provisioning.
