The fact that you had to employ the modifier "completely" to make your point suggests that the headline's use of the verb "censor" was defensible.
Their post was obliterated. Could not be found. Ceased to exist. The DMCA take-down notice removed TechDirt from Google. TechDirt was erased.
All completely true if you don't require modifiers to be stated. I'd prefer that HN doesn't turn into a tabloid.
Whether it's alarmist / excessive is subjective. And, since either would be technically correct, it probably has more to do with implied meanings or the common use of a word, and not the dictionary definition. Their usage of it is certainly defensible, but that has little to do with whether or not a modifier would make it more accurate.