AI bots are technological marvels. To think! We've imbued blips and blops with a semblance of sentience, turning code into pseudo-autonomous agents that can chat as they run around a virtual world. Unfortunately, people have been using this power to spew racist bots into Team Fortress 2. Players report seeing these bots enter their games, deploy game-breaking hacks, and spam the chat with racist slurs.
Valve haven't explicitly acknowledged the problem, but they have introduced some measures that might help.
The reports are widespread, so it seems safe to say that yep, this is a big problem. According to Kotaku, bots have been popping up since early this year, but they only went racist in the past few months.
In the patch notes for an update that landed two days ago, Valve detail new restrictions on "certain new accounts". It's not clear exactly what makes this kick in, but targeted accounts will be prevented "from using chat in official matchmaking modes". It does seem like there's a risk that some free-to-play accounts will get lumped in with the bots, which sucks. But then so do swarms of racist robots. They also say "work is ongoing to mitigate the use of new and free accounts for abusive purposes".
Some players have even banded together to form the "TF2 Hacker Police", though their impact is dubious. They're apparently trying to combat the bots by promoting the use of weapons that are particularly effective against them, which is kooky but doesn't do anything against chat spam. More effective measures include an autokick config, but the the racist bot propagators responded to that by developing a workaround and actively targeting the autokick's creator. The perception seems to be that the Hacker Police were doing little, and that interference from Valve was overdue. From the sounds of it: yes. Yes it was.
I do wish Valve would just come out and say 'yep, racist bots, we're on it', and I wouldn't say I'm grateful to them for recognising they've got a responsibility to deal with this crap. Valve recently confirmed that "hardly anyone" is working on TF2 anymore, but still. Shutting down abusive, cheating, racist bots needs to be a company priority, even for a 12 year-old game.