Ladies, this comes up a lot and I would very much like to know what you think the term "man up" means and why do you use it as a pejorative?
I, personally, would not use the phrase except on a rare occasion of joking. Like if I were working out with my daughter and she got all wimpy on me and wanted to quit early, I might say that to her with laughter. It would mean nothing.
Outside of goofing off, I can't imagine a situation where I would use the phrase.
 BlueWave
                                                
                                                Level 8
                                                Feb 15, 2018
                                            
                                                
                                                    BlueWave
                                                
                                                Level 8
                                                Feb 15, 2018                                            
                                        Because we've been taught all of our lives that 'acting like a woman' in one form or the other is the ultimate insult men use against each other.
It's sexist, stupid and needs to stop but bad habits that have been reinforced for years are hard to break and even harder to maintain.
 PhoebeCat
                                                
                                                Level 7
                                                Feb 13, 2018
                                            
                                                
                                                    PhoebeCat
                                                
                                                Level 7
                                                Feb 13, 2018                                            
                                        I agree, wholeheartedly.