That’s not settled law. From your own link (emphasis mine):
Although the Supreme Court’s opinion stated that a pardon carries “an imputation of guilt and acceptance of a confession of it,”[2] this was part of the Court’s dictum for the case.[4] Whether the acceptance of a pardon constitutes an admission of guilt by the recipient is disputed.
Accepting a pardon is an admission of guilt.
Trump is trying to rewrite history so that Nixon’s acts are considered normal presidential behavior instead of criminal corruption.
That’s not settled law. From your own link (emphasis mine):
To be fair, it would be normal for trump. He’s done worse and got away with it.