"Man up" exemplifies all of that depending on context and historical usage. Usually, it's used when men are displaying sadness. Boys don't cry, remember? You better man up and stop crying. It's a term that makes men bottle up their emotions which gets displayed in unhealthy and sometimes violent ways.
It may be used by, but the term itself is more about being the model man, so these people have a fucked view of what that is. We want remove that, not a positive reaffirmation for men. Most of the use for me is when with a group of male friends trying to push someone to something positive. Like going to talk to that girl they have been talking about, or freaking quit being so lazy and play some defense. If I was in mixed company or at work I'd most likely use step up. But the former is more personal and a group bonding thing.
The second part about toxic is just bullshit. What are some examples of toxic being used in a bad way? Any term can be used in a bad way, should we remove all words?
The point of this conversation is the example. People want to label the term toxic because it can be and remove it, even though it has value. I find that toxic.