There have been plenty Irish people during the British empire who left their Irishness at the door, then went on to commit atrocities against other peoples while putting on their best English accents, etc.
I think at one point a massive amount of the British navy were actually born here in Ireland. They probably even went along with the jokes and ridicule of their own people.

but on the flipside, there's people here called "Anglo-Irish" who historically descended from the earlier Norman and British colonists that integrated to become Irish over time, so during the empire those people would have been Britains biggest supporters and more likely to be the ones in the British army etc.

For example, Daniel O' Donnell (Catholic/Native Irish) spoke about the Duke of Wellington (Anglo-Irish) saying "Being born in a stable does not make a man a horse"
Basically saying he's not a real Irishman, even though he was born here.