Whenever I see nami fans commenting on nami's beauty, they talk about nami's beauty.
Whenever Robin's fans talk about Robin's beauty they mention nami.
Seems like they are talking to themselves somehow trying to reassure themselves that they are in the right.
It's ok to prefer one over the other guys, no big deal. No need to mention that Robin is more beautiful for the thousand times, that's just subjective, it's not like a zoro vs sanji where strength can be evaluated through feats and logic.