What you say is true.
However, there are publishing style practices which govern changes that editors may make to the words of others.
Assuming that this letter was indeed submitted by a reader to a newspaper, then it would not necessarily be justified to correct a usage error. The rules for transcribing from verbal speech are different, I think, in that the listener may attribute some errors to mispronunciation rather than misuse.
If the source of the letter could be authenticated then the decision would be easier.