At that time I had a much-petted, much-abused doll, which I afterward named Nancy. She was, alas, the helpless victim of my outbursts of temper and of affection, so that she became much the worse for wear. I had dolls which talked, and cried, and opened and shut their eyes; yet I never loved one of them as I loved poor Nancy. She had a cradle, and I often spent an hour or more rocking her. I guarded both doll and cradle with the most jealous care; but once I discovered my little sister sleeping peacefully in the cradle. At this presumption on the part of one to whom as yet no tie of love bound me I grew angry. I rushed upon the cradle and over-turned it, and the baby might have been killed had my mother not caught her as she fell. Thus it is that when we walk in the valley of twofold solitude we know little of the tender affections that grow out of endearing words and actions and companionship. But afterward, when I was restored to my human heritage, Mildred and I grew into each other's hearts, so that we were content to go hand-in-hand wherever caprice led us, although she could not understand my finger language, nor I her childish prattle.
The above paragraph comes from The Story of My Life by Helen Keller in Chapter II. As for the bold sentence, I cannot really understand the italic part. It seems to be the adverbial of the whole sentence. I know the main idea of the sentence is that Helen became angry, but I can't figure out what is the actual meaning and grammar structure of the italic part, especially the meaning and function of 'on the part of...bound me'. And what's the relation between 'At this presumption' and 'on the part of...bound me'? Is bound here a predicate?