Aumann's agreement theorem should not be naïvely misinterpreted to mean that humans should directly try to agree with each other. Your fellow rationalists are merely subsets of reality that may or may not exhibit interesting correlations with other subsets of reality; you don't need to "agree" with them any more than you need to "agree" with an encyclopædia, photograph, pinecone, or rock.
Both with other people, and "with an encyclopædia, photograph, pinecone, or rock," you should ask yourself what truth those things are telling you, and in that sense you should indeed try to agree.