I've read countless anecdotes from perfectly capable programmers who not only learned, but first discovered their interest in the field, via BASIC. No language "mentally mutilates programmers beyond hope of regeneration". And BASIC probably isn't even the worst one for learning purposes.
Remember, Dijkstra was a professor and he was an expert on teaching programming. He would have far more experience with the effect he claims than I do. I hazard to guess that is true with respect to you too.
And yes he’s obviously engaging in rhetorical hyperbole in the text you quote.
EWD's quote is from 1975 which is just barely the start of the microcomputer era (the Altair 8800 came out in '75 and the Apple II in '77), so he's not referring to those. Most people writing programs would have had access to mainframes and therefore had access to multiple language interpreters and compilers I would think.
To this day if I saw 6502 assembly on a resume I'd be intrigued and if I saw BASIC I'd view it as a yellow flag.