The first friend's fears are understandable but overstated. For one thing, right wing goons are already causing mayhem. Not prosecuting Trump will only empower them. Consider this:

https://www.nytimes.com/2022/08/06/us/muslim-men-killings-new-mexico.html

This story is only the latest example of right wing rage taking murderous form.

So the argument to me that right wing goons will precipate a violent reaction is sort of moot. They already are doing so.

Prosecuting Trump is just one front of a larger war.