I was secretly afraid of him when I saw him so dexterous; but I felt morally and physically convinced that his light head of hair could have had no business in the pit of my stomach, and that I had a right to consider it irrelevant when so obtruded on my attention.
There are no more uses of "irrelevant" in the book.
Show samples from other sources
The sentence should be deleted because it introduces information that is irrelevant to the passage.
The writer should deleted the sentence because it provides background information that is irrelevant to the paragraph.