It's a business not club of friends. After Ainge, traded PP you know anyone could be traded. Especially, an undersized guard, who is injured even though he played his heart out and loved the City, but you knew he could be gone the moment he said the Brinks Truck statement.
Those trades aren't really comparable. Pierce was traded only after both he and KG agreed to be traded.
I'm dubious that the Brinks Truck statement had anything to do with any decision Danny made. Thomas' injury and the need to be a contender (due to the signing of Hayward) and the sudden availability of Irving almost certainly had far more to do with why that trade happened than any random comment about a Brinks Truck.
If Irving wasn't suddenly available, no trade happens, regardless of the other things.
If Thomas wasn't injured, no trade happens, regardless of the other things.
But if Thomas never made the Brinks Truck comment, the trade still happens, assuming all the other things.