What about "Let's add risk to strangers' lives so we can look at a comet slightly longer"?. Throw in that 'one in one million' is a number pulled from the air to represent an opinion, not calculated mathematically, and that launching probes happens multiple times, not as a once-off event. Let's keep things in perspective here.
What happens if that burnup happens over a country like Russia or China?
And if you're going to make the "well, only 5000 people would die" argument, then you've lost already. Out of the global population that live and work in buildings, the World Trade Center attacks killed fewer than 5000 people. Overzealous police shooting people in the streets? Bah, it's hardly anyone, by the numbers. Wildfire sweeps through the state, killing 50 people? Drop in the ocean compared to car deaths, why is anyone concerned? "They were going to die anyway" is a pretty callous argument that can be used against anything.
I mean, if we're arguing for science here, then we should also be pointing out the flaws in the quoted paragraph - it doesn't matter how many other deaths are attributable to cancer (and doubly so because cancer isn't a single thing anyway). Mentioning that statistic in this context is purely political and poor science.
I say all this because the process of cutting edge science is necessarily political. You see it in academia, you see it in industry, and you see it in government funding.
For that reason, his name should not be forgotten by posterity, the way it was almost forgotten by me until this thread popped up.
Additionally, one has to consider the non-plutonic fallout and its consequences of NASA as an agency and space exploration in general.
More interesting would be how to present information to reduce the outcry.
Would it be true to say that your loved ones are thousands of times more likely to die in a car crash than in the worst-case scenario of this project?
This is a stupid reason for having an outcry.