Later that day, Castroneves posted two further tweets apologizing for the remark. He said that he didn't write it or agree with it, and that his sister, Kati, was using his Twitter. She wrote on her own account taking full responsibility.
So what's the big deal? Castroneves apologized, and his sister owned up to the mistake. However, the IndyCar Series organizers didn't see it so cleanly. They put the driver on probation until June 30 for violating the sport's social media policy. Castroneves can still race, but he is under higher scrutiny for the time being. He can also appeal the ruling. You can read IndyCar's very brief statement on the probation below.
Castroneves was found to have violated Rule 9.3.8 (Social Media Policy violation).
The member may contest the imposition of the penalty pursuant to the procedures and timelines detailed in the review and appeal procedures of the Verizon IndyCar Series rulebook