This question can be interpreted broadly, so feel free to answer in whatever way is most salient to you.
I've been thinking recently that I seem to be more sensitive to it than most. To me, it signifies losing control over one's emotions, which I do not respect; and further, prioritizing one's own emotional expression over the health of a relationship, which I also don't respect, and which hurts me deeply when I'm personally involved. I realize that's subjective and am open to dissenting opinions. Also, in case it's not clear, I'm generalizing; there are times when yelling is appropriate, but I see those times as rare exceptions.