I'm interested in having conversations with people who are capable of having interesting conversations. I'm not that bothered if they are the picture of civility to me personally. On the other hand if people want to be bigoted then I am not really interested in trying to persuade them out of it with polite conversation. I'm only interested in countering their bigotry.
Everyone gets to decide what they're interested in. For myself, I'm interested in possibly learning something from someone who thinks differently than I do. I don't mean I'm interested in learning how to be bigoted from from a discussion with a bigot, but, rather, even a bigot might be able to show me something I'd never considered. Rarely is anyone 100% wrong about 100% everything.
Closing yourself off from different ideas is also a way to let those times that oneself is wrong (rarely is anyone 100% right about 100% everything) remain and become more strongly embedded within oneself. Especially when the conversation takes place on a skeptics forum. The first place to be skeptical is with oneself.
For someone who appears to be against bigotry as much as you do, it's sounds strange that you wouldn't want to try to persuade someone to not be bigoted. Now, of course, something like that doesn't happen overnight, and many times it won't happen at all. But I would hope everyone chip away where they can, and, like water dripping on a rock, change *can* happen, albeit slowly. Of course, that type of change is much less likely unless we engage.
One might also find that areas of agreement are possible. I have years of experience as a small claims court mediator, in which I have settled small claims cases just by taking the parties into a room and helping them figure something out, rather than wasting the judge's time. At the beginning of a mediation, it can seem even to mediators that there is no way these two sides will agree on anything, they are so angry at each other. But talking things out, especially with a mediator who understands how these things have to go when they do work, succeeds far more often than one might expect.
Civility is not so much a personal need as it is a necessary foundation for having a conversation in which one might learn from someone else, or be successful in chipping away.
I'm also interested in countering bigotry, and talking civilly is one way to do that. When you are uncivil, you've lost pretty much all hope of your message getting through. Defenses rise up in the other party pretty quickly. It's hard enough when you are civil to try to break through, but it's pretty much impossible otherwise.