Research by Jennifer Bosson, Joseph Vandello (both psychology professors at the University of South Florida) and colleagues has tested the role of threatening men's masculinity in aggression.
According to these researchers, men's masculinity is something that is elusive (it must be earned) and tenuous (it must continually be proven). Put differently, men can easily lose their sense of masculinity and, in turn, when it is challenged, they respond to restore it. One prominent way males try to restore their masculinity is through aggression.
So how do these researchers challenge men's masculinity?
Some studies have had men complete a bogus test of "male knowledge." They are then either given positive or negative feedback (which would be the masculinity challenge) about how well they did. Other studies have had men tie either a rope, or braid her (the masculinity threat), while others have had them use feminine smelling hand lotion.
In response to these masculinity threatening tasks, men show heightened anxiety and thoughts of aggression. Interestingly, they also behave more aggressively, such as by choosing to hit a punching bag when given the option of that or a basketball task. Men who choose the punching task also punch harder and more often when their perceived masculinity is threatened. Further, such displays of aggression, when made public, have been found to reduce the anxiety men feel when doing these (perceived as) feminine tasks.
Interestingly, if men can affirm their masculinity (e.g., by saying "I am not gay") prior to being threatened, they do not display increased aggression.
These same studies (well many of them) did not find similar results for women.
A basic hope behind this research is that by making men more comfortable/secure with their masculinity, aggression could be reduced. After all, if the causes of aggression are not uncovered, aggression will never be alleviated.
And, stepping away from aggression, men perhaps in many cases don't do things they would otherwise enjoy for fear of being perceived as feminine. So, again, if ways can be found (except aggression) to solidify men's perceived masculinity, perhaps males can be "freed" psychologically to enjoy these things.
Or at the very least, maybe we can reach a point as a society where men don't feel weird holding their girlfriend or wife's purse.
The link below gives the reference for an article that reviews all of this research in detail http://cdp.sagepub.com/content/20/2/82.short