Masculinity, especially the masculinity of cisgender straight men, is constantly under threat from femininity.
Masculinity is something so fragile, that they fear to breathe the same air as someone who is feminine, especially someone they perceive as male (whether this is correct or not).
For something seen as so weak and so inferior, masculinity is certainly on shaky ground. This ground becomes increasingly shakier the more masculine a person becomes.
It becomes increasingly fragile the closer someone gets to hypermasculinity or idealized masculinity. It becomes threatened by something as small as painted nails.
From the fascinating blog GenderTerror, written by, Lucian Clark, a feminine female to male trans man. (You heard me!)
Here is another quote:
“Transmisogyny runs rampant in society due to this idea of femininity being seen as lesser. Trans women and trans feminine people are seen as threats to the power structure, having left masculinity, are now traitors and leaving their position of superiors. This misogynistic idea of masculine superiority rests of the cissexist notion that masculinity is only male, something that only men can truly obtain. The femininity of trans women, even if their only ‘feminine’ aspect is being female, is enough for them to be seen as lesser than men. Even more so than cis women, as cis women did not actively choose (in the eyes of a transmisogynistic society) to leave their positions of masculinity. Femininity is seen as so weak, that for one to leave masculinity in favor of it, is to be absurd.”