Although I think you’re overstating and misapplying your case, Eliezer (like Robin implies, a “cynical” critique of both cynicism and idealism seems to me to yield more fruit than an idealist critique of both), I agree with Richard that cynicism is a poorer epistemological framework than skepticism.
I think it’s also worth noting that it’s a common play for status to admonish people not to be so cynical, I think because (1) the crowd seems to award higher status to people who perform optimism as a general rule, and (2) there’s an element of power alignment, and (if one is powerful) power maintenance to convincing less powerful people not to be cynical about the reasons for power variance in a social group.
I recommend being wary of a point that needs to exist as part of a dialectical pair. What’s orthogonal to cynicism vs. idealism. What’s completely outside the set? What encompasses both? What has elements of both? What subversive idea or analytical framework is muted by discussing cynicism vs. idealism instead? I think these type questions are a good starting point when a dialectic is promoted, in general.