I am a person that speaks up. I didn’t for a long time, but around 5? 7? years ago, I registered that not saying or doing something is kind of bullshit, and I’ve been working on it since. It’s a perpetual work in progress.
In any case, I tend to go for the straight-forward approach.
Dudebro: *says or does sexist thing*
Me: “Whoa. Nope/ Hold on there/ Hang on. That’s ain’t cool/ That’s not ok/ That’s sexist, bud”
Dudebro: *tries to rationalize action/statement and/or leans into it*
Me: I hear you, and I’m telling you that what you did/said is still shitty and sexist, and here is why. *explain why*
Dudebro: *sticks to previous statement*
Me: *Reiterate previous points*
[continue until they get it, or they shut up and leave the situation]
I’ve found being calm but firm, and standing my ground if and when I’m told to ‘calm down/not be an sjw/it’s just a joke/etc’ will for the most part shut people down. Most people don’t know they’re being shitty, and those that are generally aren’t expecting to get called on it due to social contract. If you break social contract and face them on their shit, a lot of people back off.
I also try and make sure that they understand that I’m not calling them sexist (even if they are) but what they said or did as sexist. It helps the person receiving the critisism not feel it’s a personal attack. If you attack the person, they’ll shut right down, but if you attack the action they are generally more willing to listen.