[HenryLeeII]

Had Davis been tried he would have been convicted, no other outcome would have been conceivable to the Johnson administration.

...or no other outcome would have been allowed...

[Non-Sequitur]

...or no other outcome would have been allowed...

Of course not. The jury would have certainly been made up of Unionists who would have voted to convict based on the evidence the government provided. Why would you find that so surprising?