IMO there's a tendency for those on the right, in whatever country, to support whatever the military does, right or wrong. This is just my personal opinion and I'm perfectly willing to be contradicted, but the impetus for criticism of military "over-zealousness" (if it's your lot - war crimes if it's the other side) tends to come from the centre and left.
At least in the UK, it's the Conservatives who have been pushing forward legislation to prevent ex-service personnel from being prosecuted:
https://www.bbc.co.uk/news/election-2019-50372932
IMO the actions of the Trump Administration over Gallagher is just business as usual for the right wing - especially if it's overpopulated by chickenhawks attempting to overcompensate for their lack of service.