But it doesn't end with this. The problem with the strategy "define what is acceptable and politely exclude those who don't agree" is that it is a recipe for keeping the marginalized marginal. Some of the straight white men of tech don't live in a reality where women and PoC are equally good at understanding technology. Some people are die-hard racists or sexists. Some people think gay marriage is wrong. They aren't doing it because they're evil, they're doing it because they sincerely believe they're right and others are wrong.
Your goal cannot be to directly change somebody else's definition of acceptability, or force them to change their rules. The supreme court agreed that gay marriage was not a constitutional right in 1972 before reversing itself in 2015. It's not because the court is fickle. It's because the court is made of people, and those people in 2015 came from a different place than those in 1972 did.
It's very difficult to change individuals, or the spaces and institutions they control. What is practical is creating an alternative space, with rules you like better, and letting everyone who agrees in. Over time, if it's a good space, it will grow, and out-compete the other place. The individuals in your space will make their own way into institutions. One day, quietly, you'll discover the majority of those institutions are controlled by those who agree with you, and they will change the rules.
So don't yell at people whose companies aren't diverse or whose online forums are racist, sexist cesspools. It's pointless. Make your own diverse, safe, inclusive company. Make a better, more popular forum. Don't waste time trying to convince people diversity is worthwhile. Make it obvious, by making your space better than theirs.
But this is still too pat an answer. What if you're so marginalized the resources to make your own space aren't available? You can't get funding, or you don't have the skills to compete because no one will mentor you?
I don't have a good answer, but the answer from history is that there have always been those in the in-group who used their positions of privilege to fight for the marginalized. You fight for your own rights, and before you're even done getting them you turn around and offer a helping hand to the people having an even harder time.