At a very small startup, people are going to expect to have to work hard. While I disagree that this absolutely necessitates a lack of work/life balance, let's say for a moment it does. Sure, you're probably only going to be attracting people who are interested in working as much as possible, in a high risk/reward scenario. In some cases that's also going to be selecting for single people who have no children.
And that's fine, for the most part. What's not fine is engaging in exclusionary behavior related to diversity of gender, race, sexual orientation, etc. E.g. it's not fine to have a bunch of white employees who make racist jokes at work, or a bunch of men who talk at work about their sexual exploits, or a bunch of straight people who marginalize homosexual candidates during interviews.
My initial reaction to the parent's assertion of "any non-zero subset of reasonable people are so offended by a behavior that they'd leave the industry because of it" was also negative, because it sounds super absolutist, and PC (in all the actual negative ways "PC" has been used), and an indictment of being your genuine self. But really it's just about keeping stuff out of the workplace that has nothing to do with work. If work is about building products and figuring out how to sell them, and you focus on that, it eliminates a lot of problems. That doesn't stop you from being friends with people at work, but it does mean you might want to keep certain conversations away from the workplace, and instead have them on your own time. It really isn't that hard, as long as you're committed to examining your unconscious biases and eliminating behaviors that stem from them, at least in the workplace.
Right. And fixing what you described is a good thing. But - if you think there would be no reasonable people disliking tech and leaving it - that's not going to happen. As for "offended", this word is used now pretty much in any context - one seems something he doesn't like, he's "offended". Maybe once it had some special meaning, like being sexually harassed at work, or being fired or disregarded at work for having skin of wrong color... But now people are "offended" by Shakespeare, by algebra, by clapping hands, by Christmas, by marble statues, by Thomas the Tank Engine, by burritos and by hoop earrings (all real examples, I can find links) this no longer has any distinctive meaning that can be singled out. So we can just accept some people would dislike some stuff and leave, and that's fine. Not everybody in the world should work in tech. We should strive to provide environment free of obviously bad behavior - like harassment or racism - and then if other stuff that happens in tech does not work for everybody, it's fine.
> it's just about keeping stuff out of the workplace that has nothing to do with work.
That'd be nice but I'm afraid that ship has sailed - tech is getting politicized, and if you believe what you hear about companies like Google, Facebook or Twitter, you can replace "getting" with "has been". It's not a good thing, but it's a thing. That's not the reason to dig deeper and make the situation even worse, though, by undertaking unachievable PC-driven goals.