While it sounds very proper to say, don't us all caps, it's sort of sleazy, low-class writing, I've seen it done by good writers. I would agree that a better way to do it is say that someone shouted or emphasized or bemoaned something. Then there's no doubt what emotion your character is emoting, and you don't have to stoop to using upper case letters.
However, and it's a huge however, writers and their writing need to be flexible. What if, for instance, you've just strung a bunch of 'he saids' and 'she complaineds and 'they crieds' together in a row, and now want a statement made without attribution? So you write something like, Jack turned around and saw Mary coming. He was seething with anger. "You BITCH! You left me there, stranded! WITHOUT ANY PANTS!" Now I don't want to modify or weaken that by adding a 'Jack screamed, red in the face.' I want to leave the statement bare and intense and hot. The best way I can think to do that is just as I show it. Using caps. There's no question what they mean, and if you're getting your intent across to the reader, I see no problem with doing it. Occasionally.
I think in much of writing, it's difficult to always obey hard and fast rules, like never use caps to show emotion. I thoroughly agree that one shouldn't rely on it. There are generally better ways. But occasionally we have to be able to write outside of the rule box to create the effect we want.
C