One thing I really can't stand, is 'urine mints' - the bowl of mints or candy that they have in receptions at restaurants. Imagine the number of people who don't wash their hands after using the toilet and then put their hands in the bowl.
The problem with lice is not cleanliness, it is people are not doing what is needed to eradicate them. This is a huge problem because if you don't get rid of them completely, then they will spread, and quickly! Also, if you use pesticidal shampoos to treat them, but don't get rid of them completely, then you will end up with a resistant strain of lice, which is also a huge problem. For lice, it is totally necessary to nit-pick!!