It's worth reading the Wikipedia entry on the following report and Feynman's findings. Anonymous polling of engineers showed they estimated a general probability of catastrophic disaster in a shuttle launch between 1% and 2%.
So latimes.com's article blew it out of proportions.
2% chance of disaster is not nearly the same as "so certain was he that the shuttle would blow up."
You're conflating two different estimates: Boisjoly was certain that the particular launch would fail, and a survey of engineers gave a 1-2% estimate for failure across all flights.
Both of those predictions turned out to be extraordinarily accurate.
