I think there's a lot to be said for NT detachment. ENTP's I think can really highlight what this means because on the surface, ENTPs and ENFPs can both seem very sociable, gregarious, and 'nice'.
But, NFs are more ego attached and place more importance on their own feelings and the feelings of others and pretty much embody an ocean of feeling. ENTP may consider everyone's feelings, but it's more strategic or analytical and not necessarily empathising. So the analyses of the same situation and their involvement can be VERY different.
As far as the comment that ENFPs can be crude and mean in their arguments (I disagree) and ENTPs present ideas in a charming way, I think detachment and misinterpreting people's intentions may come into play.
It's REALLY easy to be charming and sociable consistently when presenting an idea because you don't really care either way about it nor really invested in the people and easy to seem vicious when you are personally heart invested in something.
This is not a dig at ENTP but in general, I don't take too many pitches very seriously. Everyone has their own agenda and just because someone is polite or charming doesn't mean they give a fpersonal fuck about you, if anything, they are just good at what they do and more concerned about getting their point across, making the sale, convincing people they're awesome, caught up in enthusiasm, what have you.
Maybe it's because of the fields I'm naturally drawn to - entertainment, politics, sales, etc. -- but seriously, don't take what you see on the surface too seriously.
But generally to get to the real substance and the heart of the matter sometimes you just can't package that nicely or be slick about it. I think this is where the cries of NT callousness and jerky behavior and NF hysterical blood-letting come in.
Maybe ENFP moreso than ENTP is ready and able to get "down and dirty" with things because we see that as a necessary part of life and a given when you care deeply about things. I think for many NTs either that seems crude or unecessary. They prefer the strategic detachment thing or else they are capable of being ruthless but simply don't see it as beingn ruthless. They place place no negative value on the emotional fallout or hurt they may cause because they're looking at it from a totally other angle (their own) and everything else is secondary or inevitable.
I think it's true though that if an ENFP is being extremely cutting, it IS intentional and they ARE aware of it. However, what you intepret as viciousness may very well just be an ENFP getting very enthusiastic about something in our own way and we aren't intentionally trying to hurt someone or being personal. I guess you'd have to ask the ENFP. I've said this elsewhere but ENFPs can launch brutal personal attacks but we won't because that's generally totally against our values.