I've spoken about the Slashdot crew at great length in the past. I don't know if those comments have survived the recent server crash though, so it can't hurt to recap.
The Slashdot crowd are victims of a confluence of factors. They are largely engineers who have no training within the history or philosophy of science. They have a tendency to treat science as a cult (accurate predictions have no relevance to belief) and an arrangement of facts that can only be sorted out only by qualified individuals. More often than not, they lack a realistic view of the problem of the inferential step. These people tend to be prolific consumers of space sciences entertainment and over-the-top futurist predictions. They typically do not realize that what drives them to observe all of this is in fact little more than a sense of wonder (as opposed to an objective and careful search for truth). In other words, they are more likely to be astounded by a spectacular difficult-to-believe announcement than to wonder at whether or not it's in fact true. Controversy plays only a limited role in their views of science.
The people there tend to be highly pseudo-skeptical and idealistic in their views of peer review. They expect that any theory that challenges the mainstream should only be considered if it cannot already be explained by current theories. But what they don't realize is that this belief constrains their own ability to understand or judge the competing theories. Most of the time spent debating these people is spent convincing them to read things. Few arguments will actually base upon a discussion of the actual evidence. In other words, nearly all of the EU critics there have failed to read an actual book on the Electric Universe; when they do read one, they will oftentimes read it for the sole purpose of discrediting it. They look at the Thunderbolts webpages, and then claim that they shouldn't believe EU Theory because there is no long list of peer-reviewed journal articles at the end. They will oftentimes claim that the Electric Universe is not supported by peer review without apparent awareness of IEEE's yearly plasma cosmology publication. They will oftentimes advocate some proof for the Big Bang (like the CMB) without any awareness of any alternative interpretations.
Much of the problem is that most of the people there do not trust their own abilities to judge arguments related to space. You will frequently see the phrase "IANAP" (I am not a physicist) -- or something similar. Oftentimes, as in the case of Arp, they will allow scientists to convince them of things that can quite clearly be observed with their own eyes to be false, and they will permit this solely on the scientist's credentials. They have an unfortunate tendency to publicly ridicule people who appear to have a nuanced view of science, or who do not agree with conventional wisdom in some way ("cranky"). This serves as an unintended feedback loop too, since newbies who observe this ridicule will unconsciously internalize this over time to mean that they too will be ridiculed if they deviate in their beliefs from the mainstream. This is proven by psychological studies.
When posting on Slashdot, it's better to present some strong arguments and ask poigniant questions than to confidently assert some sort of knowledge. Also, be aware that most people will stop reading the comments section within a couple of days of the thread starting. I recommend including links to sites other than just http://www.thunderbolts.info
To get the attention of the people there, it will be necessary to break the aura of invincibility surrounding conventional wisdom in science. Eric Lerner's device could actually pull this off. So could cold fusion, but that technology requires another $100 million to productize.