If I remember correctly, he tested positive on a diuretic and the Brazilian federation basically only warned him, whereas normally athletes would have an actual doping ban.
Correct me if I'm wrong of course, but since then I didn't like him - apart from his whole "look at me being a victim of everything"-look
When I was at the swimming world championships in Barcelona, I was there all week and at each and every victory ceremoney, but only for Cielo I could and did not applaude when he won or stand up for his anthem.