Rationalizing bad behavior is an NF thing? NFs are somehow better at it? Humans rationalize bad behavior. It's theoretically conceivable that an NF with Fi may use morality to do it (although I've never seen anyone do this... perhaps you should give me an example of it). That doesn't in any way raise the stature of this thread above bitter rant. I also hope your own baggage hasn't led you make such vast generalizations, or so-called tenedncies that embrace INFPs, ENFPs, INFJs, and ENFJs.
...
Points:
1. Everything I've posted (or will post) in this thread has been generalization with consideration to both groups of people and tendencies. I'm often misunderstood as saying things "are..." as opposed to saying things "often tend to be..." It's the latter.
Check out the bold/italic/underlined portion. You weren't misunderstood.
2. It is also primarily detached, abstract analysis in the INTP style. The analysis is its own goal. I might as well be discussing a mental creation as actual people.
As a P, I can go with that.
3. I would say NFs have less of a need to rationalize than others. To use function terminology, their dominant judging function is Feeling, so if something strikes the NF as right, it will likely forever be considered to be right. There is less of a felt need to make excuses for actions. SFs tend to be less influenced by the concept of chasing ideals, and therefore show dissimilar inclination here.
If by "feel" you mean see whether or not an action fits into your value-system, then kudos. Otherwise, you're probably confusing Feeling and feeling.
For my own clarification, are you assuming that
A) NFs are behaving badly because their F tells them to. IOW they genuinely believe they're doing the correct, morally just thing.
B) They're repressing their F function. This is something you could theoretically attribute to ENFPs or INFJs simply because feeling is not their dominant function (thus easier to ignore).
C) It's self-delusion. IOW, they're manipulating their F function to justify what they want to do. (similar to repression except you're corrupting the F instead of ignoring it)
I ask because when you say Fs don't TEND

to need to justify their behavior, you're suggesting repression. However, then you say in point 5:
5. All types can demonstrate behavior similar to this. As stated earlier, it is the method of justification which is somewhat unique.
and supporting point 5 is your example in point 4 where:
They have followed their heart, and feel justified in doing so, which leads to...
(where "followed their heart" is the justification. Iow, they value following one's heart)
Those are in conflict, so I'm confused.