If they would just stay where they were supposed to be, and not invade another country, then we don't have a problem. We didn't attack them, they attacked us first.
And what business did we have entangling ourselves in their civil war? You basically admitted they were attacking S. Vietnam and not the US
The policy of containment. They attacked an ally of ours.
No one is disputing that, that does not mean we did not provoke them. Helping someone's enemy on their home turf seems like the textbook definition of provocation
We stayed in S. Vietnam, so it wasn't their turf.
To the irredentists (and, mind you, they had ample reason to be irredentists), being there was ample reason.