But he specifically used the word "blockchain." I'm making two claims: first, that blockchain-based systems (for most people's definitions of "blockchain" other than a meaningless buzzword) are worse for people in situations like that of the "African farmer" than centralized systems, and second, that the vast majority of Bitcoin detractors dislike it specifically because of things related (directly or indirectly) to it being a blockchain-based system.

For instance, "Bitcoin is a bubble" only makes sense if it's its own unit of currency. "M-Pesa is a bubble," "Square Cash is a bubble," etc. aren't meaningful statements to make; they just support transmission of the underlying currency. ("Kenyan shillings are a bubble" is a meaningful statement, but I've never heard anyone claim that you should use cryptocurrencies to insulate yourself from hyperdeflation of a fiat currency.)

"Bitcoin is environmentally dangerous" only matters if proof-of-work is relevant; in a centralized system, you don't have the problems that lead to you wanting to even consider proof-of-work.

"ICOs are a scam" doesn't make sense in a centralized system. "The transaction rate is too low" isn't a complaint anyone has about a centralized system (the usual complaint about the US markets is that the transaction rate is too high, and HFT should be throttled). And so on and so forth.