So they should be condemned for their idiocy, not praised for it. Their odds aboard the ship were demonstrably infinitely better than on the planet, after all.
A dying ship offered no safe haven. You would have condemned the crew to death. In the moment, beaming to a planet (not being consumed by the DDM at that time) was the better option.
Which is demonstrably the opposite of truth - using a starship for ramming finished off the beast, while using a shuttlecraft achieved nothing at all.
As FormerLurker pointed out, the Constellation was not used for "ramming" and it is clear that without Decker's successful run, no one would have dreamed up a way to destroy the DDM. They had no idea how to stop the DDM until Decker's run. No getting around that.
Which is besides the point anyway: if the DDM cannot be defeated, then it doesn't matter whether Starfleet even tries. But tagging along and trying is the way to go if Starfleet doesn't specifically want to wuss it out and let the UFP die.
It is the point--your point; "Tagging along and trying" produces no results. You seem to be handing out "A for effort," but in a combat situation, fruitless effort (a conclusion they reached with the ineffective Phaser attacks)--again--produces no results.
He lied to make the death of his monstrous friend look more heroic. That's simple enough, and perfectly in character.
To pretend that he believed in what he wrote would mean stating that Kirk is stupid. Not my preference here.
Kirk based his report on the man Mitchell was--the real man--not some changing creature who--as Spock predicted--
he'll have as much in common with us as we'd have with a ship full of white mice.
The Starfleet officer was not that creature, and despite your need to damn the entire life/character of the man--was not demonstrated as having any traits that would lead to the post-barrier character. The point of Kirk's episode-long shock and sense of tragedy was the night and day contrast between the real Mitchell and the altered being.
I don't have to. No court on Earth would even allow for you to ask the question in the first place. If a murder takes place, "he didn't show signs of it beforehand" is not an accepted argument and no defense.
I'm not sure what trials you have witnessed, but behavior before the alleged crime is often used to paint a picture of a defendant. This is not some Limbaugh-ian "born guilty--the end" system of justice.