Saying "I disagree" does not say what the person would prefer instead. It creates a non-natural cluster of people preferring various kinds of alternative solutions. A list of choices would give more information. For example "moderator should ignore it completely", "moderator should use a private message to suggest retracting the comment", "moderator should move all related comments to a separate discussion", etc.

In that way the people who think there should be a specific basilisk-related thread with trigger warnings don't end up in the same set as e.g. the people who think the site should be completely unmoderated. (And maybe we could get a result that most people think Eliezer should have done something else, but there is no general consensus about what specifically it should be, so it is likely that if Eliezer had actually done something else, he would still get a lot of criticism. You can't get this information by posing a dilemma of "I agree" and "I disagree".)

Alternatively, I'd like to have an answer: "I don't fucking care. Forever obsessing over a one-time event that happened years ago is more harmful than the event itself." Which is connotationally completely different from both "I agree" and "I disagree".