The pushback has been part of a growing trend amongst MCU fans to react extremely strongly whenever the integrity of Marvel films is questioned or threatened.
For fans, it was the way Scorsese dismissed Marvel movies after admitting to not really having watched them in the first place that was particularly unfair.
There are a lot of Italian-Americans that don’t think he should be making films about them like that.
It is certainly true that Scorsese has come under fire in the past for the inaccurate portrayal of Italian-Americans in his films.