Is that what happened? I don't know, but I'm not going to trust two tweets from two parties whose interests are against one another.
Why do you, what's the reasoning behind that kind of law? And to whom do they petition - does the company have to agree, or rather, does the employer have the right to forbid employees from forming agreements between themselves? It sounds counterintuitive when you only need 1 person to start a company, or 2 people to have a contract, and when employers have no other control over who employees meet with and little control over how employees spend money (e.g. 'work dress code').
source: https://www.nlrb.gov/rights-we-protect/whats-law/employees/i...
Besides, there may be many people who think having a union is always a good idea, so they would sign without thinking about it much.
In this case, the employees coming out with this knowledge have everything to lose because they could easily be blacklisted from further jobs. Kickstarter has no reason to not deny their accusations and has everything to gain from it.
If someone is risking a their livelihood to say something like that, then perhaps we should take what they're saying with a larger grain of truth. Otherwise we'd be saying that whistleblowers and the PR arm of a company have exactly the same weight.
If a few months from now, I read an article about what just happened now and it turns out that the company ends up being fined or something because the motivations behind firing him are actually what he claims, then it's the moment we can start being outraged, not before.