I can certainly relate. For someone of a temperament that often seems quite cynical and harsh, I relate a lot to the idealistic side of things. My morality tends to be quite simple and forgiving (mercy over justice any day), and is something that is ever-present, if at a reduced awareness to other aspects of my life. I attribute this to tertiary Fi.
And I do have a tendency to sort of...write people off, sometimes. Certain acts that I deem to cross the line can taint my image of a person ever after. It's something I actively resist, because a part of what I take to be moral is the recognition that there is no such thing as a purely evil person; generally, everyone has their own moral perspective and I should try as hard as possible to understand their act from their own framework.
So, while I have this tendency, I resist it in real life cases. It's a lot easier in fiction. I love fiction with all kinds of moral grey zones, but sometimes, a character just does something that makes me say 'that character is evil,' and I'll often think of them that way thenceforth.
I definitely think that INTJs tend to have an internal moral code that is extremely significant to them. I know that I have mine, and I will not act against it. It makes me stop to move worms from the footpath to the grass after rain, or to flip beetles right-side-up when I see that they have become upside-down and can't fix this themselves. I'm not sure how far it extends, but I do frequently do things because I take them to be morally necessary, despite the fact that, intellectually, I don't believe there is any such thing as objective morality.