The US flag condoned slavery for 88 years. The Confederate flag (which that tatt isn’t) only condoned it for four.
But in those 88 years, if a State wanted to outlaw slavery they had the right to do so. Under the Confederate Constitution, the states did not have that right
The “confederate flag” is a battle flag. Curious the Marines are upset about a tattoo of the battle flag. Anyone who is upset about it maybe shouldn’t be in the Marines to begin with. They’ll see a lot worse things than that if they stay a Marine long enough.