“Although comics have been in existence for over a century and a half, they suffer from a considerable lack of legitimacy. To those who know and love it, the art that has given us Rodolphe Töpffer and Wilhelm Busch, Hergé and Tardi, Winsor McCay and George Herriman, Barks and Gottfredson, Franquin and Moebius, Segar and Spiegelman, Gotlib and Brétecher, Crumb and Mattotti, Hugo Pratt and Alberto Breccia, not to mention The Spirit, Peanuts or Asterix… in short, comic art, has nothing left to prove.”
His critique of this is that an analogy to literature would be ridiculous: why would literature have anything to prove?
However, we can take this one step further. In his work, Gröensteen conflates the socio-cultural "comics" with "sequential images with/out text". If he means the former part of this dichotomy (comics, the sociocultural phenomena) then Domingos' argument stands. If he means the latter (the expressive system of sequential images), the claim becomes even more bizarre:
Why would any type of expressive form (drawing, writing, etc.) need legitimation? Do we really have to have justification for why drawings (in sequence) are worthy of attention at all? From a cognitive perspective, this seems crazy: all of these things are just ways in which humans express themselves.
To exemplify this, try replacing some of those names above with friends of yours, and the last sentence as: "in short, English, has nothing left to prove."
The justification of English should be self-evident, and so it should be with the visual language of sequential images too.