Clinton has never been a boy so doesn't realize we learn at a young age that  if we sit with knees pressed together, feet splayed laterally,  we get called a "puss". .  Sitting with knees apart is comfortable, and not rude if there is space for everyone .     
Insulting men for everything, especially just being guys, is why Trump won.   This kind of ridiculous critisism and widespread misandry is why we went nuclear on femminism w our Trump votes.  You can't tell "The Donald" how to sit. 
Guys today are being raised to be totally self concious.   I noticed some  millenials wear golf shirts with the top button bottoned, untucked shirts and so called shorts to mid calf.    Uncomfortable.    Does Clinton want a male burka? She wan't to make guys   feel self concious about EVERYTHING, but it's not gonna work.  It's like Adam Carolla says: In 50 years, we'll all be chicks.  Hope not.