He implied that Bottas did something "incredibly dangerous" because of who Russell is, you can't get more arrogant than assuming someone is racing you harder than anyone else. Especially when what Bottas did was just the normal thing in defending, you take the best line and squeeze your rival without pushing them off track or changing direction suddenly - Jolyon Palmer's analysis
here does a great job illustrating this and why Bottas did nothing egregious or wrong.
And it was a massively unfair thing to say, hence why Wolff went in on him as hard as he did.
The fact that it was in the heat of the moment is why I mentioned his apology - saying things you regret happens, especially in F1. Hamilton, Vettel and Verstappen have all had to apologise for stuff they've said about other drivers in the past and I don't really hold it against them too much, likewise with Russell here.