I agree with Ramya that Edmund is dense and rationalizing rather than arrogant in dismissing Fanny’s concerns. (:D) He does not dismiss them outright; he has reasons and explains them. There is an element of the instructor in his explanation but I think his motive is a pure one of helping her understand the situation as he sees it and of course (mistakenly) believes he is correct. I don’t see that he has an ego too big or too fragile to accept Fanny could be right and he in the wrong despite the fact he formed her mind (7).

Edmund took on the role of mentor out of kindness and generosity because she deserved the attention:

He talked to her more, and, from all that she said, was convinced of her having an affectionate heart, and a strong desire of doing right; and he could perceive her to be farther entitled to attention by great sensibility of her situation, and great timidity. …Kept back as she was by everybody else, his single support could not bring her forward; but his attentions were otherwise of the highest importance in assisting the improvement of her mind, and extending its pleasures. He knew her to be clever, to have a quick apprehension as well as good sense, and a fondness for reading, which, properly directed, must be an education in itself. (2)

Following Ramya’s lead I also point to Ch. 16. (:D) Edmund does want Fanny’s blessing for his decision to act in the play and he is disappointed not to get it. He says “If you are against me, I ought to distrust myself” and it seems to me he does distrust himself. I feel he knows that he is rationalizing doing wrong (acting) for somewhat commendable reasons but in his heart realizes they are not quite good enough to outweigh the multiple improprieties of the entire acting scheme. He wants Fanny’s approval to feel better about a decision he knows to be on shaky ground:

“Give me your approbation, then, Fanny. I am not comfortable without it”.