The main argument against prosecuting Donald Trump — or investigating him with an eye toward criminal prosecution — is that it will worsen an already volatile fracture in American society between Republicans and Democrats. If, before an indictment, we could contain the forces of political chaos and social dissolution, the argument goes, then in the aftermath of such a move, we would be at their mercy. American democracy might not survive the stress.
More generally, a favorite pundit belief is that there are "divisions" that must be "healed" through Grand Compromises that appeal to pundits (but few others) and through the regular atoning for the sins of powerful people by the masses, granting the powerful forgiveness and absolution.
None of this ever makes any sense. People disagree about stuff, there are not "rifts" that can be "healed," and the regular absolution of rich people is the cause of, not solution to, our problems.