He never made the argument that goto was considered harmful (the title was not his), the letter itself is a solid argument for why the unbounded goto (as opposed to the, typically, function or lexical scope restricted goto) creates programs that are hard to comprehend. He also, if you read the letter, does not argue for abolishing goto, it's part of the larger case of going toward structured programming.
If you learned programming after about 1990 (probably some time in the 1980s was the real inflection point, but by 1990) you would have been learning structured programming and the argument was moot, because it had won. Every major language used after that time (outside of assembly languages which are inherently unstructured as a language) was already using structured programming so the argument seems superfluous or you end up having people compare the goto he describes to the modern restricted goto, which is not something he would have (strongly) argued against (though certainly against its overuse in some cases).