In the Book of Mormon text, we consistently find the expression “to be angry with someone” (50 times), never “to be angry at someone” (the more expected expression in modern English). There is one example of “angry at” (in 2 Nephi 33:5), but this passage refers to being “angry at the words which I have written”.
Here in Alma 19:21, Oliver Cowdery initially wrote down “angry at” in the original manuscript, then immediately erased the at and overwrote it with the beginning wi of the preposition with; then finally, without crossing out the wi, he wrote inline the whole word with. The critical text will maintain the consistent use of the preposition with in the phrase “to be angry with someone”.
Summary: Follow in Alma 19:21 Oliver Cowdery’s immediate correction of “angry at” to “angry with” in the original manuscript.