The high school I went to cared a great deal about students accepting responsibility for their decisions. There was an honor code and various rules to reinforce the need to think about one's actions. One of these rules was the "In The Presence Of" rule.
This rule was fairly simple and straight-forward, leaving little room for interpretation. Basically, if you were in the presence of someone breaking a rule you were just as guilty as they were even if you were not participating. You're chatting with someone smoking behind the gym, you're getting treated like you were lighting up to. It was your responsibility to either discourage certain activities in your presence or leave those performing them to themselves.
I bring this up because there are professional contexts where this concept is pretty useful. Certainly this is true in instances of misconduct, but I'm specifically thinking about sexual harassment. If you think this isn't still a problem in science, you might just have your head up your ass. I hear several stories a year about a female scientist being subjected to some form of inappropriate conversation from a (usually senior to them) male scientist. I've seen it in action and even been directly confronted with this stupidity.
Whereas I am all for women standing up and calling out this kind of bullshit, it's naive and a cop out to lay this responsibility entirely at the feet of those at the wrong end of the power dynamic in these interactions. If the goal is to stamp out indecent behavior by male scientists, then other male scientists are in just as much (and better, in many cases) of a position to do so. Which brings us back to our high school rule.
Dudes. If you are in the presence of someone making a woman uncomfortable with their conversation, gestures, physical contact, etc., and you just let it go, you are as guilty as the jerk is. Find a way to let your colleague, be they senior or junior, know that their behavior is not acceptable. It's neither easy or comfortable, especially if you are caught off-guard, but watching it happen and doing nothing is just another way we promote harassment around us.