I guess it’s affirming to think that people reject one’s ethical outlook because it would necessitate such an awe-inspiring commitment or burden. Rather than for more analytic reasons.
(Edit: reading my first post, it's definitely the case that I did not make the connection here explicit- the rejection isn't merely 'oh no I can't handle the TRUTH', but more like, 'ugh, these guys'. A big part of it is social in nature, stacked on top of the underlying problem of asking too much.)
A huge part of EA is driven by analysis of effectiveness. If I want to be effective, I have to figure out how to be effective. If someone provides a valuable insight on how to be more effective, it's not a rejection of my ethical outlook, but rather useful information.