If I'm honest, I think how people view the severity of his mistake depends on how much they like him. I remember when Lingard made that social media mishap last summer, the criticism he faced was huge and snowballed further into the season. Pogba also has a lot of microscopic criticism of his every move, and he doesn't even do anything scandalous really. The reason why these two attract a lot of criticism is that some people just don't like them, and they are unable to answer on the pitch (in Pogba's case due to injury).
I think if people were to admit Grealish made a bad mistake, but they like him and thus don't care about the mistake, that's more honest than downplaying the severity of the incident. As we've seen on the site, we don't need much to really pile on, hate on, micro analyze, and overcriticize players, provided we already don't like them.