Actually, yes there is a ranking for most disgusting poo to step in and I think it has to do with the number of diseases and parasites you can contract from the poo. For example moose poop is ok. It's usually dry & full of plant material. I don't mind stepping in it. I'm sure you can get diseases from it but I can't name any off the top of my head. Human poo could be full of Hepatitus A & E, Amoebic Dysentery, HIV, giardia, Rotavirus, E. Coli, Norovirus, Tape worm, and a number of other worms, bacteria, viruses, blood born pathogens, etc. Given how hard it is to stay healthy in places with poor sewage & waste treatment practices, I would personally prefer to recreate where people aren't dropping deuces. Why continue to spend tax money on city parks if they are just going to be used as giant human litter boxes?