Except, unless you're a naturally benevolent person (most people aren't), being polite usually does cost something, even if that something is a bit of time and brain cycles. The cost also stacks, and paradoxically increases as your project grows from your niceness.
In the course of business, that politeness is paid for with money in the form of risk of churn. Yet for much of open source, nobody is paying or incensing the maintainer to be polite and "considerate". Asking a volunteer FOSS maintainer to be polite is more or less asking for free work, on top of the free work they're doing by giving you software.
I actually think the problem of sexism, discrimination, and unwelcoming in FOSS is intimately tied to the fact that most FOSS is not meaningfully being paid for by its users.