I respectfully disagree. If Trump is going to argue that the president is “absolutely immune” from prosecution for his “official acts,” which is exactly what he is claiming, then just how far that goes is a legitimate line of questioning.
If the president does have that immunity, then assassinating a political opponent who poses a “clear and present danger to the republic” is arguably within a president’s official responsibilities to defend the Constitution against all enemies, foreign and domestic. If the Supreme Court agrees, then given the election interference the Biden administration is already engaging in, Biden is likely to decide that Trump could be killed and Biden could walk away with impunity.
Never give to your political friends power that could be used against you when you are out of power.