Hard for me to say, since I have that knowledge, but I wouldn't think its necessary.
I was raised Catholic, even went through the trouble of getting confirmed. I have always had a strong interest in science, and was determined to find something supporting at least the notion of a higher power/intelligence. I argued about it in, of all places, a video game forum (different one) with the token local open atheist. We had some pretty heated (you've seen my style, he was more or less similar

) back and forth, but he at least made the comment that I seemed to have a better grip on science than the other believers he argued with.
At the same time, I was shooting down some fellow believers that were wandering into the thread that were taking a similar stance, but with what I felt were really sloppy arguments that I didn't want to be associated with. I wound up taking an interest in the debate as a whole (intelligent design vs modern biology, primarily). It took probably four or five years before I eventually both came to the realization that there WERE no good arguments in favor and came to accept the argument that beliefs in things I could not support meant which of those things I chose to believe versus others was completely arbitrary.
So there's an additional bunch of useless information you didn't need.

Back to the point though, I never felt that that knowledge has really helped me much, other than knowing why people were protesting something before reading why later in the article and arguing with believers, which I almost never do now anyway.
I think you can probably get along fine without it, and your professor was thinking you need it to understand other people's motivations. People have all kinds of motivations, very few of which we understand. Typically, religious motivations are called out specifically in any article covering news stemming from them anyway.
I do think though, that coming from a religious background makes people more likely to be better atheists. It can probably make them more likely to understand why people are and remain religious and less likely to think that believers are just stupid, which I don't think is an accurate or helpful way to look at it. It's certainly not necessary in order to have that kind of view though, either.
"What I really don't understand is what kind of recipe do you want because you talked about porn, phones and cooking and I became lost" - Vega
"Fate loves the fearless" - James Russell Lowell