They don't condone recent behaviour from some players.
For those who don't know, the Kuala Lumpur Major competition for Dota 2 is currently being held by PGL as the first Major of this season, with some of the top teams battling it out for supremacy, although Valve has taken to the game's website to talk about the responsibility players have with their words.
"We expect pro players to understand that they represent the Dota community regardless of where they are. Words carry a lot of meaning. Some people may not agree or understand why certain words are harmful, but it doesn't make it any less so to those on the receiving end. The language used by multiple players over the last week has caused many of our fans a lot of pain and is not behavior that we condone."
"We've been spending the past few days talking to various pro players and community leaders about this. From all the interactions we've seen over the years, we know that deep down professional players respect each other immensely. However, we want to be very clear that Valve will not tolerate racist language between pro players in any form. We think it is really damaging to the entire Dota community whenever even a single professional player uses discriminatory language. It pits fans against each other, belittles and demeans entire groups and makes them feel like they are not as important. Going forward, we expect all teams who participate in our tournaments to hold its players accountable, and be prepared to follow up with strong punishments when players represent Dota and its community poorly."
"We hope that players and the community around the world will become better educated and more respectful as a result of the recent incidents. We think the communities everywhere around the world want the same things: for our favorite players and teams to do well, and for a great display of Dota."
As reported by Dbltap, there have been a few incidents in quick succession recently where slurs have been used, and Valve seems to be making sure that pro players know that they can and will be held accountable for what they say at all times.