You've overthinking and not in the right direction so I'll try to help out as best I can. As before, I don't think the posted meme expresses itself well.

None of the people saying "Liberty" here came to power for an extended period. They lead actions against oppressive groups, slavers, settlers etc. They don't need this violence justified by the precedent or the framwork of their oppressors, not least because they were left with no other choice but violent action.