If any non-zero subset of reasonable people are so offended by a behavior that they'd leave the industry because of it, we have to cut it out.
So don't ask "would this bother me?" Ask "would it bother someone?" And since you can't predict this from inside your head, you have to rely on firsthand accounts of people being bothered. This seems like a good overview of such accounts.
That's a very high demand. People can leave the industry for a very wide variety of reasons, often mutually contradictory - some want to work as much as possible, provided it translates to $$$$, some are ok with earning less provided they can pursue side interests or family life, some want to make worldwide impact and break paradigms and change the world, some want quiet, predictable and organized workplace, some want high-risk/high-reward environment, some want benefits of predictable income and steady promotion... It is literally impossible to make an industry in which there would be nothing that would cause anybody to leave. Tech industry not special - some people may try it and find it's not what they'd like to do anymore and leave.
Surely, if some things bother people and we could reasonably fix them without bothering even more people in the process, then there's no reason not to do it - it'd be a positive-sum action that would make the world better.
But pre-committing to a goal that no non-zero subset of reasonable people ever wanted to leave tech does not seem like a smart thing to do, because it's impossible.
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.