Men who are frustrated about women only wanting to be friends are heavily criticized, told they're entitled, manipulative and they are generally subject of ridicule and anger.

Women who are frustrated about men only wanting to have sex are comforted and told he's a scumbag. There's even a relatively new, socially acceptable slur for such men: fuckboy. Additionally, this frustration is commonly published in mainstream media, with "where have all the good men gone" and "men are commitment-phobes" being entire subgenres of gynocentric journalism related to this phenomenon.

Anyhow, how are these attitudes any different from each other? Both want something from the other gender that party is not willing to give and feel sad/angry about it.

Also, how does this work together with the "it's just sex" attitude modern women often have? Suddenly, the sex she "gives" the man is all-important again and him refusing a relationship means he "used" her. That directly subscribes to the "sex devalues women" line of thinking.