When is the right time to talk about it?

I've been talking about this all over FB, Twitter and Yahoo! groups, so excuse my brusqueness.
I took Jade and O to the library for storytime. I was just trying to fill our morning with a quick activity so that the kids would take an early nap, so that we could go swimming with friends in the afternoon.
Anywhoo, so we go to storytime and the librarian picks up the book Freedom Summer by Deborah Wiles. I'm thinking, okay.....never heard of this book, what's it about. Then the librarian reads the author's note. Sidenote- are you even supposed to read the author's note to the kids? Here is an excerpt from the author's note....

Also in the summer of 1964, civil rights workers in Mississippi organized "Freedom Summer," a movement to register black Americans to vote. It was a time of great racial violence and change. That was the summer I began to pay attention: I noticed that black Americans used back doors, were waited on only after every white had been helped, and were treated poorly, all because of the color of their skin ... and no matter what any law said. I realized that a white person openly having a black friend, and vice versa, could be a dangerous thing.

Okay, I'm thinking to myself, 'are you kidding?' I want to leave but I don't want to cause a scene and getting Jade to leave storytime before the story would definitely cause a scene. The librarian starts reading the story and it's all about two friends, one white and one black. After the passage of the Civil Rights Act, the town pours tar in the town pool rather than allow black people to swim in it. Is it just me or is this a little, um, heavy for story time?

I have a lot of issues with this.

1. Shouldn't there be some sort of warning if the subject matter is going to be uh, sensitive?
2. Isn't it my job as a parent to determine when and how I want to discuss sensitive topics with my children?
3. The slave trade, American slavery and the Jim Crow period that followed are very serious, very....what's the word I'm looking for.....layered, multi-faceted...deep. I think that conversations like these deserve more than a 15 minute story time. This would be an ongoing conversation in my house, but I don't want the library forcing my hand.

So, I want to hear from you. Tell me what you think. Am I overreacting or am I right that this was not a great choice for story time?

And while we are talking about it, what hard topics have you addressed with your young kids? One woman on Twitter told me that she had discussed Prop. 8 with her three year old. Uh, wowza!