How can I transform this sentence into active voice (from passive)

This is the sentence that I want to change but I cannot think of a way to do it without changing the meaning of it.

My father did not seem to be bothered by their insolence as he taught, but I knew that deep down, he was very morose.

take out "to be"

thanks. yeah i didn't think of it, and it still sounds well

No, no, this is the way to make it active:

Their insolence did not seem to bother my father as he taught, but I knew that, deep down, he was very morose.

You make it active by switching it around. Can you see how it feels more powerful this way? That is why the active voice is better. Good question!!

oh i see now. well thanks to both of you. I've always had problems with this.