Here's a concise answer that straightforwardly applies the rule I already stated. Since my rule only applies above 50% and since P(being shot)=10% (as I recall), then we must consider the negation. Suppose P(I will be shot) is 10% and P(I will be stabbed) is 10% and suppose that (for some reason) "I will be shot" and "I will be stabbed" are mutually exclusive. Since P<50% for each of these we turn it around, and get:

P(I will not be shot)is 90% and P(I will not be stabbed) is 90%. Because the cost of being shot, and the cost of being stabbed, are so very high, then the threshold for being convinced must be very high as well - set it to 99.9%. Since P=90% for each of these, then it does not reach my threshold for being convinced.

Therefore I am not convinced that I will not be shot and I am not convinced that I will not be stabbed. Therefore I will not go without my bulletproof body armor and I will not go without my stab-proof body armor.

So the rule seems to work. The fact that these are mutually exclusive dangers doesn't seem to affect the outcome. [Added: For what I consider to be a more useful discussion of the topic, see my other answer.]