Does anyone today have trouble understanding that species can go extinct? Do you see people standing up, declaring that this is simply not possible?
Well, in the 1800s, people did. A lot of people took issue with this idea, other scientists included. Part of the argument was that one couldn't prove that a creature wasn't around any more, because they could simply be hiding in some unexplored region of the world. Okay, maybe. But extinction theories also flew in the face of religious beliefs about the world, the same way that evolution is considered to conflict with the Bible today. If God created all forms of life and placed them on earth, how could they simply go away? It wasn't part of the plan, the design.
I think the idea of extinction conflicts with the Bible more than evolution does. Evolution only conflicts with the Bible if you are really into the literal "days" that it took for God to do everything. Both the Bible and evolution explain that the world started with the seas, the earth, the sky--and that eventually we had fish in the sea, birds in the sky... and eventually people. (Okay, the Bible neglects archea, bacteria, fungus, viruses, and protists, but I'll let it slide.) The only thing up for discussion is the issue of time. So really the only people who can't deal with evolution are still into the week-long creation and the earth-is-6,000-years-old stuff. Eh, we'll get there.
But extinction really throws a wrench in everything. Because, neglecting the details, the Bible explains that God put all living things on earth in a very thoughtful, controlled way. Extinction completely contradicts that idea, because it means that things are a bit more random, and that a type of creature placed here with such care could just cease to exist. Woah. People took a while to be able to swallow that idea, but now it's common knowledge.
I like to point out this past controversy to show that while people may get their undies in a twist about an idea and what it means, time has a way of smoothing out the wrinkles. For the current "controversy," evolution, I think the time-iron just needs another generation or two to smooth those undie wrinkles out. So many have already found a way for religion and science to coexist (or some, like me, just don't worry about religion too much). Understanding takes time, and that's a-okay.