I offer no defense of Github's choice. What do you think was the reasoning for their decision?

I can understand the concern about powerful organizations imposing a viewpoint surreptitiously via a widely-used piece of software. That is definitely a reasonable fear, and if we allow concentrated power (MSFT here) to behave in that way, then we are in for trouble.

I'd argue that we wouldn't end up with tyranny, but rather feudalism. There are other powerful organizations that can push their own viewpoints, surreptitiously and overtly. It then becomes a game of who has the most resources and control over the flow of information. But while I prefer "feudalism" to "tyranny", I don't disagree that if propaganda was the aim here, it would be a bad thing.

I don't agree that GitHub's aim was to impose a viewpoint. I believe the aim was to avoid putting this tool in the middle of a very politically charged issue. For example, how do we know GitHub didn't make this decision like this: "We don't want 8 genders popping up in a <select>, because that will offend the 50% of the country who only believes there are two". We are seeing some evidence of this (and the other 50%) in this thread.

Finally, maybe they are trying to prevent people from spamming their learning model with politically-charged content. If that were the case, you could argue that they are just trying to prevent their programming tool from becoming a political warzone, with competing sides trying to train their viewpoints into the model. I admit I know very little about ML in general and Copilot in particular, so you'll have to bear with me if that sounds naiive. In any case, social media is an example of a tool that has become a political battleground, even though that wasn't the initial purpose. If preventing Copilot's politicization is GitHub's aim (and I have no evidence that it is), then I'd say that's a reasonable thing to want for product if you don't want it to become unpleasant-to-use before long.

So we have three hypotheses:

1. MSFT believe there are more than two genders, and want to impose that viewpoint

2. MSFT believe there are only two genders, and want to impose that viewpoint

3. MSFT wants to avoid having politically-charged content in their code-generation tool.

How can we point to one of these being more correct than the other?

I don't have any evidence to support any of the three. But 1 and 2 each make three assumptions (MSFT has one viewpoint on issue X; this viewpoint is Y; they want to impose it). Hypothesis 3 makes two assumptions (Gender is politically charged; let's avoid that in our product). That's all I can think of this late at night. I could be missing something.