The thing is, as some other people have pointed out, the guy is not a native english speaker, and many latin based languages simply don't have any gender neutral pronoun and make use of the neutral masculine instead. Many of these languages have seen some people propose new ways to handle pronouns to change that recently, most of which are somewhat controversial. It's easy for a native speaker of those languages to assume the same is true in english (especially since the use of "he" as a generic neutral is, as far as I can tell, still valid, although clearly out of fashion). Once you take all of that into account, the proposed change can easily be viewed as someone trying to simply push one of those controversial ideas instead of a widely accepted generic masculine, which would clearly fall into politics in the sense of "real world beliefs and social issues irrelevant to the topic at hand". The rest seems to simply be a pretty childish ego war between him and some mastodon users which could have been solved by either side taking 5 minutes to explain their point of view on this matter.

Now, even without this context, from what I can tell, the issue at hand was a single instance of " he" used to describe a generic anonymous user in the dev VM... Seeing that as unprofessional because it addresses someone as male by default surely is a bit of a stretch.

About that "no code for rivals", I don't think is as stupid as many mention. Right now when it comes to web browsers (at least ones with wide compatiblility and features), there's only 2 choices : chromium-based and firefox. So someone trying to bring some fresh blood is welcome, and in order to avoid having the same issues as the chromium-based ones, you need to make sure you are not overly dependent of your competitor's code. Granted, this is a pretty strict approach, but it doesn't prevent them from using the same libraries and techs, it just means that any code written specifically for a different browser shouldn't be copy/pasted.