What kokaino said was not that temazepam is guaranteed to kill everyone, but that "Adding alcohol with over 2000-3000mg of temazepam will kill you" which may still have been a bit of an exageration if you take that to mean will kill 100% of people, even those with insane tolerances, but if you can look past the hyperbole there is actually some truth in the other points kokaino made about temazepam.
Temazepam is more dangerous than other benzos. Temazepam has the highest rate of intoxication, both on its own and with alcohol, compared to other benzos. Studies done (at least as recently as the late 90s) showed temazepam to cause more overdoses than other benzos and for the overdoses to be more likely to be serious (comas, fatalities, etc). It was also shown to have the highest number of deaths per million prescriptions (which I think means that the fact that it was more widely prescribed in the 80s-90s should not be a factor since they are going by deaths per million prescriptions and not just comparing the numbers of deaths total). Temazepam is less euphoric than other benzos, so people may take more to try to achieve euphoria. As with many drugs, tolerance to each effect of temazepam can progress at different levels, so a person could be tolerant to, say euphoria or anxiolysis but not coma or respiratory depression, which can be dangerous for obvious reasons. And adding alcohol (as with other CNS depressants) can vastly increase your chances of death. Unlike most benzos, temazepam is not affected by individual variations in the P450 enzyme system, so it can be hard to make an equivalent conversion estimate from other benzos the person has taken, as the equivalent dose of another benzo can vary greatly from person to person.
I agree that scare tactics and exaggerations are counter-productive, we are a harm reduction site after all, but I do think it is fair to say that temazepam is an especially dangerous benzo and to use appropriate caution, especially with high doses or when combining it with alcohol/other drugs.