IMO, there are simply too many quiet students for them to all be suspected as abnormally or imminently violent. "Quiet" kids are one of the most basic kinds, so that alone wouldn't likely be enough to spur a blacklash. You'd have to be quiet, creepy and rude, all the time, in order to stand out as seeming Cho-ish.
I am glad that even the news media's suggestion that Cho could be autistic will certain spur more autism research, because much, much more needs to be understood about autism in general, not to mention Asperger's Syndrome, about which virtually nothing neurological is known for sure. I don't want to be "cured", and I certainly don't want a forced "cure". But I do want more study on what it is that I have. As always, greater public knowledge of this will be a mixed blessing.
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Christianity is different than Judaism only in people's minds -- not in the Bible.