The validity of your statement seems to hinge on how one scopes "rational" or "logical" when describing the action of someone, say overcome with emotion. If one views emotion as (part of) a preference function that (to use very loose analogies here) determines/selects which microtheories are appropriate for a given stimulus, then one can maintain rationality modulo emotions. They become part of a process which conducts a radical reassessment of the primitives of the theory. Sort of an additional factor in determining when one hops from one part of the lattice of theories to another. 

Yet within the reordered primitives, there is some rationality. There is some logic in actions of one seeking revenge for a love betrayed. True, from a different, longer-term or humanist perspective, it might not be a desirable reaction; but it is only from the granting of these assumptions that the thirst for revenge is deemed irrational. Within the bubble of anger fuelled revenge (perhaps even nominally with an appeal to 'an eye-for an eye"), some logic still pervades, no?