While not in any way condoning racist chanting, I think Rudiger shares the blame by getting Son sent off with a ridiculous reaction to Son's feeble kick. His behaviour was provocative.
If the Spurs fans had confined themselves to booing Rudiger, it wold have been acceptable.
The elephant in this room is there is no way Rudiger would randomly notice one racist amongst the other 50,000 fans shouting vociferous abuse at him. People are so naïve.
Rudiger knew he had made a cunt move. He was in survival mode. He also knew that riling that many spurs fans, the odds of some being racist was near certain. He knew exactly what he was doing. He deliberately kept an eye out, as soon as one of the fans bit on his hook, the job was complete.
Have to admire his genius.