Something which people don't always recognize about open source is how "value-capture" works for creators. FOSS eschews direct monetization (selling licenses to the core product) based on an ethical premise (it's unfairly limiting to end-users) and/or a business premise (the ecosystem is a key to the value prop and licenses would slow down the ecosystem growth).
None of that means that the creator isn't capturing value. You capture social credibility and market awareness which you can convert in a variety of ways, including monetarily (by selling complementary products/services, by donation models, or by getting a job that you might not have had the career-credentials to get otherwise). As an aside to elaborate on this point: a lot of the recent debate about paying FOSS maintainers has to do with projects which realized all the potential social value-capture, and left creators with an externality of maintenance.
Intuitively, I think people understand that forking and rebranding a project without a really strong motivation can be scummy, but I don't think people can verbalize why. This is why: you're attempting to steal the upside which the creator is the in the process of capturing.
And FWIW, anybody saying that a blogpost is weak action and you ought to be going to court is ignoring that, when the value you're capturing is reputation, then public discourse is the tool you want to be using to manage it.