I think you're reading a bit too much into it. Casemiro praised a young player, that could've been anyone out of Garnacho, Antony, Pellistri, Malacia really. I do think he said that because Antony is going through a bit of a dry patch after a good start, but that doesn't really mean there's much more in it.
There's a lot of talk about negativity, abuse etc but is it really the case with Antony? I don't se it here, and on social media there are always some haters.
On the bolded part, actually he's been better recently, also praised by Ten Hag post match so he seems to be heading the right direction.