IMO, the issue here is that Microsoft appears to have violated the MIT license requiring inclusion of the original author's copyright notice. I think he has every right to be salty about that violation.

In your analogy, the sign on the furniture says:

Free, but if anyone asks, you got this furniture from .

Microsoft took the furniture from the curb, but isn't telling people whom they got it from.

I agree in regards to your opinion that he shouldn't be complaining about the fact that someone forked his project, that just the nature of the MIT license. However, I do think he is justified in being upset that the license was violated. Hopefully this gets remedied; it's not hard nor expensive for Microsoft to add his name to the copyright notice in the license.