Alright, 他人にはダメって言う人がやりがちな事 means, Naysayers are a far too common occurrence for others.
I assume the problem comes with the やりがち, which alone means something along the lines of, likely, common occurrence, often, etc.
puts on tinfoil hat they didn't actually die because the missile lands in front of the wall and you have a higher chance of surviving since missiles don't contain shrapnel and artillery shells don't look like that