You can either try and sway people purely philosophically as the software freedom conservancy is trying to do here, but I think ultimately in today's world, you need more, most of the time, you need to show that:

- what you opposed negatively affects your target audience in real ways that matter, for their career, livelihood, or some other means

- Show that continuing to be apart of an old model will be damaging in the long term

- Also importantly, the thing you are referring people to do needs to be seamless. For instance, they mention SourceHut, and I sure hope SourceHut has all the core features and ease of use of GitHub, because if not, you are likely already going to lose in this conversation to most

Without factoring these things, its great to point out issues, and rightfully they should, but its not going to mean much in terms of action