Much better to call it on him now rather than letting him go through life not knowing how to spell. Sure, wait until he’s humiliated the next 50 years because he can’t get a decent job because he didn’t learn a thing in school.
Oh he should have been called on it. Just not in the forum. Spelling can be very difficult for some people and it really is not a from of lack of intelligence. Even rote learning does not help. For some learning to rely on the dictionary is the best answer. Helping a student learn to use the resources available so he can provide the right word spelled correctly should be a given. Cause as you point out it does matter.