Or as an alternative, he could have privately emailed an existing contributor, discussed the change, and got support. If it had come from Isaac or Bert to start with, it would have sailed through without objection.
I really feel like a pull request was the wrong vehicle for what the original submitter was trying to accomplish.
If open-source projects adopt an "email first before pull request" approach, I think that's a big mistake. That will mean a lot of dialog with people who aren't actually going to do the work, and a lot of missed patch opportunities from people who have done or will do the work but are put off by the uncertainty of a policy like that.
Regardless, if a pull request is the wrong vehicle, then the correct response isn't, "Request rejected! Go away." It's "Let's talk about this more." It was a two-line change that made the project better. (At least, nobody has so far claimed that the gender-exclusive language was better.) I think that's enough of a positive signal to be worth following up on, and certainly not the dire insult that some believe it to be.
Ok. If it's not a policy, then I don't think there's any way you can expect a potential contributor to know that a particular pull request must be preceded by discussion. In which case, I think the burden falls on the person reviewing the requests. In this case, Noordhuis. The submitter did their bit by making a positive change and offering the patch.
I really feel like a pull request was the wrong vehicle for what the original submitter was trying to accomplish.