While I do share the author's frustration with the fact that GitHub does zero fact checking, my concerns go entirely in the other direction: much of the internet now works in such a way that a DMCA takedown notice will effectively remove any content someone doesn't want out there.
I do understand why platforms do it like this, being in the business of arbitrating who is right and who is not is not feasible (and it's probably also not legal).
Criticisms of this process should be levied against lawmakers and the law itself.
However, to be perfectly frank, it's a good thing that hiring a lawyer to send this letter on your behalf is the minimum effort required to do this. Of course that doesn't solve malicious takedown notices sent by big law firms and corporations, but I do believe it limits the overall amount of letters that get sent.