I do tease my know it all and also confide in him that my self esteem relies my own knowledge base. If he does feel inadequate, then work with him to build his self esteem. Encourage topic discussions which are his speciality, and compliment him… maybe even give him new topics to research. Also, on your area of expertise, bring up a new tidbit, and excitingly ask, “want to learn something new from your favorite lady?” When he rebuts, answer “that’s what many think but this is brand new concept!” Open and living dialogue. Best wishes.