A problem with this line of reasoning is that there is a potentially infinite number of issues, all of which could affect you or someone vulnerable. However, people have issues that are more immediate to them and which they have a more direct responsibility over. For example, If I don't personally champion solutions to police brutality, someone else might, but if I don't do my job and earn a living, there isn't really anyone else who really can or should be expected to pick up the slack.What's more, peple need the mental space to think about the issues that they are going to take a stand on which means that it takes time and energy to address different issues and they need to prioritize. This is one reason why it's reasonable to restrict political discourcse to certain spheres, because doing so is necessary if we are to take into account basic human limitations.

So why aren't these vocal GitHub employees leaving the company then?

If this was really about strong political will they would just change companies.

If we follow their own logic, they are enabling ICE by continuing to work for GitHub and are thus complicit.

Not entirely true. The essence of the libertarian platform is a political platform that tries its best to ignore you as an individual and let you be free.

If libertarians were running things, you'd be left not entirely but largely alone.