Re: One could argue that I [and Bostrom, Rees, etc] are blowing the issue out of proportion.

Bostrom and Rees have both written books on the topic - and so presumably stand to gain financially out of promoting the idea that existential risk is something to be concerned about.

It could also be argued that we are probably seeing a sampling bias here - of all the people on the planet, those with the highest estimate of DOOM are those most likely to alert others to the danger. So: their estimates may well be from the very top end of the distribution.