I agree. The best strategy for Plant would be to keep a low profile, and avoid provoking Canelo. Trash talk never works in the ring, as we have seen from numerous cases earlier. All that said, I am not sure whether Plant made the statements on his own. Sometimes the organizers want cheap publicity and they ask the fighters to make such controversial statements. IMO, I don't think that it is fair to blame Canelo for the positive test from Oscar Valdez. That said, Alvarez tested positive for Clenbuterol in 2018, which he claims to have come from eating contaminated meat.
This controversy is just temporary, once the right is over, eventually, they will stop talking and people will forget. Lots of doubts when the fight is easily beating his opponent, just like during the prime of Manny Pacquiao when some think he is unto enhancement drugs, but it was not proven.