Well, I think that's just my point, insofar as I was making a non-facetious point (which isn't very far, after all): while spearfishing is a 'sport' in the sense of 'physical recreation', it's not a 'sport' in the sense of 'athletic competition between individuals or teams where the same rules apply to both sides.'
So it seemed a little disingenuous for my acquaintance to suggest that by spearing only as a freediver he was making things 'more sporting', i.e. more of a 'fair contest' (which is what he seemed to be implying) - from the point of view of the fish, the distinction is likely trivial, because the contest is distinctly one-sided. If my acquaintance had said something such as, "I spearfish only while freediving because it makes the hunt more challenging," OK, fine; I wouldn't have any reason to raise an internal eyebrow.