I don't see much of telling these generalizing people that not all Christians agree. It seems like if someone has already decided to go the route of assuming that all Christians think the same, they're not going to be convinced by one or two Christians claiming they 'disagree'. They could always rationalize that as them lying to save their reputation.
Besides which, I don't think that a Christian needs to explain himself to someone who's already decided that all Christians are lawbreakers any more than an atheist needs to explain himself to someone who's decided that all atheists are babykillers.
Negative assumptions do not grant you a special right to make other people explain themselves.
No they don't but if you're saying you hate those negative assumptions then maybe you should do something about it.
That's exactly what I'm doing here, isn't it? I can't go to each individual person on a case-by-case basis and refute every single misconception they have. I can, however, convince other people that those people should be held accountable for their generalizations. Slander and libel are really only dangerous if people accept it and don't think for themselves. If people think "Wait, he hasn't got any evidence to back that up", they've made the first step to realizing that the first person is, in fact, full of it.
In case you didn't notice the first person to make any comment about these people giving Christians a bad name was GOatmaster himself. If he dislikes that Christians get a bad name cause of these idiots then his choices consist of sitting there annoyed about it or getting up and doing something about it.
If he wants to do the former then that's his choice but if some minority was giving FS2 players, or British people or atheists or any other group who I was a member of a bad reputation you can bet I'd point out that they were dickheads who didn't represent me.
Or he could simply ignore it and move on. The Discovery Institute's ability to disseminate ID is aided by public attention. If the DI can turn things into a 'public attack on Christianity' because it's getting trash-talked by a bunch of people online, it'll just help it gain sympathy and support. If, on the other hand, it's simply handed a lawsuit by Harvard, it's nothing but a case of copyright infringement and plagiarism.
They could never have done that if the majority of the Christians in the country had simply said "Shut up, you're talking bollocks" but that isn't what happened. The vast majority of Christians said nothing. It was left to the atheists and a small percentage of vocal Christians to say that ID was bull****. The fact that the majority of Christians didn't say anything allowed the Discovery Institute and their friends to present the whole thing as an assault on Christianity instead of what it actually was, an attempt to try to bring religion into science classes via the back door.
No, it's the people who believed them who are at fault. They made the assumption that the DI represented the majority of Christians, and they were wrong. (EDIT: Though if the DI actually did claim to represent the majority of Christians, I'd say that they were at fault, for outright lying.)
So this isn't a simple case of Christians unfairly getting a bad name due to the actions of a few. They are getting a bad name due to their own inaction. And that bad name may be deserved. We'll never know now just how many Christians were quiet because they believed in ID and how many were quiet simply because they couldn't be arsed. I tend to feel that the majority were actually of the latter group but while the majority say nothing we'll never know.
All that kind of argument does is benefit the DI, because they can claim a greater association with those Christians. It also helps them stir up action from those Christians, because now they've got a bunch of people criticizing not just the DI, but those Christians who have done nothing but stay out of it. So instead of getting Christians to stand up for you because they've come to an educated decision, you're more likely to get them to come back with a knee-jerk defensive reaction.
You can't force people to care. If you think you can, I'd suggest you talk to politicians - they've had centuries of experience at trying to do just that. But even they haven't been able to get much voter turnout most of the time.