there's plenty of racist comments as well in that reddit thread that filtered the chat of pro players in pub players, targeted against a divers list of nationalities/ethnicity. Not just against Russians.
I think you're missing the point. Yes, there is plenty of 'random' trashtalk aimed at every nationality / race / sexual orientation going around. But 'AngryGerman' or 'Pizzaboy' isn't likely to get spammed with FUCKING GERMANS / ITALIANS FUCK YOU YOU ALL SUCK GET OUT OF MY SERVER because some guy lost his promotion match, whereas 'VodkaBro123' will almost certainly start getting flamed from the moment they feed away a random death and well into the post match. I don't think you realize just how toxic DotA is towards Russians specifically nowadays -- and enabling more of that by pro players is the last thing this game needs.