Imho, Trump does not lose his temper easily. I think his expressions in this regard are to distance himself from the DoJ results so he cannot be accused of using political power to go after his “enemies”. Of course the demshevik revolutionaries will so accuse, but this is for the general public.
That could very well be the case. But there was genuine anger in his comments tonight. That doesn’t mean there isn’t also a purpose behind it.