Nephi shows incredible spiritual maturity for his age. He is able to discern between the promptings of the Spirit and his own human emotions. Surely he would have been angry at Laban for the way he and his brothers had been treated at their last encounter, but his anger does not enter into the decision making process at any point.
Nephi is left to struggle with which of the Lord's commandments he should keep. He had been taught not to kill yet the Spirit was urging him to take Laban's life. He had to make a choice between two apparently conflicting commandments. Fortunately, this kind of spiritual conundrum is a rare occurrence. Adam was placed in a similar situation in the garden after Eve had partaken of the forbidden fruit. He could not "multiply and replenish the earth" and "not partake" at the same time. In these rare spiritual conflicts, one should follow the example of Nephi and Adam and choose the better of the two options, being 'led by the Spirit' (v. 6).