I don't think you can really compare the poisonous emissions of diesel exhaust leaked materials from a reactor.

I see your point, any nuclear excursion tends to get blown out of proportion, but it does have some unique dangers.

In particular, diesel fumes eventually dissipate, whereas radioactive materials will settle and continue to be a problem for decades. Which may not be a problem if it's left alone, but anyone unlucky enough to interact with it could end up with it on their body/clothing unaware that they're absorbing an unsafe dose over a period of days or weeks.

But yes, I agree, we do need to move away from fossil fuel sources one way or another.