My random advice from the internet:

In the context of the other recent thread: https://news.ycombinator.com/item?id=12011012 This course of action should run by a lawyer.

Overall, framing this as a purely business matter rather than one of morals/ethics/justice might be useful. My intuition is that there is money set aside to purchase the domain and a timeline for acquiring it. If there are millions of dollars for a law suit with uncertain outcomes, there is even more for a certain quick outcome.

Anyway, there's nothing to be gained by treating matters as personal or evil regardless of what they might be.

Good luck.