I have a tough time digesting the legumes I've eaten in the past, and I won't even eat them in small amounts.  In fact, some bean extracts are used as thickeners, and even these sometimes bother me.  It certainly may be true that a diet rich in legumes and high quality olive oil is a lot better than a typical American diet, but that does not mean it is optimal.  And keep in mind that saying "legumes" has no scientific precision, though that is what "nutritional science" is based upon (that is, these kinds of abstract categorizations).  For example, some legumes can be strong suppressors of the thyroid, while others are not.  The scientific (and practical) thing to do would be to test out very specific diets and see what the effects are.  Also, if you are getting enough high quality protein and other things you need, while avoiding dangerous items, like corn oil, then having some legumes in the diet may not cause any problems.  As I said, I can't seem to digest them well at all, but perhaps you can.

Oh, as to "proof," remember that is for math and logic, not these kinds of situations.  Here, all we can do is examine all the relevant evidence and try to make sense of it in a coherent way.  As I've said before, I think it makes sense to compare specific diets against each other, because the "nutiritional experts'" way of categorizing food items can be very misleading, and in the case of lard, is downright ludicrious.  Here is some evidence:

 

Titre du document / Document title Nutritional significance of lectins and enzyme inhibitors from legumes Auteur(s) / Author(s) LAJOLO Franco M. (1) ; GENOVESE Maria Inés (1) ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s) (1) Departamento de Alimentos e Nutrição Expérimental, Universidade de São Paulo, Avenida Prof. Lineu Prestes 580, CEP 05508-900, São Paulo, BRESIL American Chemical Society, ETATS-UNIS Résumé / Abstract Legumes have natural components, such as lectins, amylase, and trypsin inhibitors, that may adversely affect their nutritional properties. Much information has already been obtained on their antinutritional significance and how to inactivate them by proper processing. Chronic ingestion of residual levels is unlikely to pose risks to human health. On the other hand, the ability of these molecules to inhibit some enzymes such as trypsin, chymotrypsin, disaccharidases, and α-amylases, to selectively bind to glycoconjugates, and to enter the circulatory system may be a useful tool in nutrition and pharmacology. Trypsin inhibitors have also been studied as cancer risk reducing factors. These components seem to act as plant defense substances. However, increased contents may represent an impairment of the nutritional quality of legumes because these glycoproteins and the sulfur-rich protease inhibitors have been shown to be poorly digested and to participate in chemical reactions during processing reducing protein digestibility, a still unsolved question.

SOURCE:  http://cat.inist.fr/?aModele=afficheN&cpsidt=14353437

And:

"Lectin may contribute to the atherogenicity of peanut oil."

Lipids. 1998 Aug;33(8):821-3.

Read the abstract of this study at: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9727614&dopt=Abstract

Thank you for your response.

 

Perhaps this topic could be situated in the "Nutrition" section better than here, if you want to move it. Excuse me for that.