It has nothing to do with men and women, except specifically the in-universe lore of marefolk, whose men are uncontrollably aggressive and libidinous.
IRL I don't think people with Y chromosomes are universally more libidinous or dominant than those without, even if cultural sexism makes it more acceptable for them to be. But talking specifically about one fictional race in a fictional game, marefolk males are uncontrollably horny to the point they're either thrown out of the tribe altogether, kept chained up as breeding stock, or magically altered to let them control themselves. The enchanted armour you steal and give to Brint was created to reduce the aggression of uncontrollably aggressive people, in addition to feminising them. Applied to Brint, who has functional levels of aggression, it reduces his aggression/dominance to below normal levels, in addition to switching his gender.
