The bad behavior of one person does not excuse the bad behavior of another. Each individual is responsible for their own actions and should be held accountable for them regardless of what others have done. Attempting to justify or excuse one person's bad behavior by pointing to the bad behavior of someone else is a logical fallacy known as "tu quoque" or the "appeal to hypocrisy."
In the example you provided, it would not be reasonable or logical to use Donald Trump's bad behavior to excuse or dismiss Bill Clinton's misogyny. Similarly, attributing Donald Trump's behavior as a "cure" for President Biden's cognitive health issues would be unfounded and illogical.
When discussing the actions or behavior of public figures, it is essential to evaluate each individual separately based on their own merits, actions, and statements. It is also crucial to rely on credible sources and evidence when making assessments about their behavior or health.
Political debates and discussions should focus on substantive issues, policies, and ideas rather than trying to use one person's behavior to deflect attention from another's actions. Constructive discourse is key to addressing societal problems and promoting a healthy democracy.