Referencing Twitter as evidence of workplace toxicity is just dumb tbh.
Twitter is a personal page for your own opinions etc, and if you're 'toxic' as an individual that's fine. As of yet, he's not tied to a brand, and can say shit if he likes. Sure it might affect them picking him up, but if if you're looking at him to hire him, you could easily just say "you'll have to cut the BS on twitter though".
If someone joins an org and is therefore brand associated, they will be told to calm their shit on social media as it can harm a brand. Anyone with half a brain should have the common sense to do that. 'Toxicity' is only bad if it becomes a behavioural issue in the team or in terms of Riot punishments.