When you've pretty much agreed that everything he said was true (though you attempt to handwave it away
Fearmongering about risks that are statistically insignificant should be waved away. Otherwise one would hardly ever leave their own homes (or even move about in those homes).
and blame the victim...
Noting that the well-known cases of violence within Couchsurfing.com related to single females hosting single males is in no way blaming them. Rather, the point is that since the GP is presumably male and writing for a predominantly male audience (these being the sad demographics of Slashdot), his exortation to fear such violence is groundless.
The "years of experience" you cite are for more-or-less closed communities of like minded people, very likely known to each other or having common friends or acquaintances. The modern hospitality exchanges are between random people, complete strangers.
There has been no such transition overall in internet hospex from trustworthy closed communities to "random people, complete strangers" as you depict. Couchsurfing.com specifically has grown too large to have that feeling of being a closed community of like-minded people, though the result of this is vastly more likely to be simply meeting a person whose company one doesn't enjoy with than experiencing crime. However, internet hospex in general remains a series of overlapping circles of friends, which one can plainly see from Couchsurfing's two community-run alternatives.