The issue isn't whether or not tanking is against the rules
The issue isn't whether or not the Blazers tanked
The issue isn't whether or not everyone knew the Blazers tanked.
The issue is that Dame gave the NBA the impetus to investigate the Blazers for tanking.
If my son drives recklessly, I'm unhappy with him. If he gets pulled over, I'm unhappy with him. If he gets cited, I'm unhappy with him.
If his girlfriend dumps him, and then sends the police video evidence that he was driving recklessly, and they begin investigating him as a result, I'll primarily be pissed at her.