I think the issue is we have years worth of evidence of Rossi doing self-serving things in GP, so it's hard not to look at the helmet design as more of the same.
I'm going to put this out here before the GP race starts.
My belief disclaimer notification***
Rossi is milking an injury that is nowhere near as bad as has been claimed because it makes him look brave to be out there competing and GP will help sell this image especially if he wins today that he overcame all kinds of pain to battle his way to victory. And well, if he loses, he has a built in excuse already to be deployed.
It's been made to sound as if Rossi is doing something highly courageous along the lines of Lorenzo riding at Assen with the broken collarbone or something of a similar nature. Meanwhile, for those of us who know grand prix motorcycle racing did happen to exist prior to the arrival of Valentino Rossi know that in the golden era of the 80s and early 90s, riders were riding with far worse injuries than what Rossi suffered. I distinctly recall both Wayne Rainey and Kevin Schwantz riding with some pretty bad injuries during the 1991 to 1993 period and there was little said about Schwantz's broken wrists or Wayne's say 1992 campaign where he thought about withdrawing completely from the championship until Doohan's accident happened. To say nothing of numerous injuries current riders on the grid have suffered in 2017 that were/are far worse.
Anyway, whether I'm right or not, who knows, and I'm sure those reading what I wrote above will vehemently disagree with it. I would add that the only reason any of this is even talked about in these terms is because of what the past behavior has indicated.
