Yes, it's a dog one.
I live opposite a green where over the last couple of days, people have been putting out there live (now dead) xmas trees, ready for collection. Looking out of my window, I see a couple walking their dog, sniffing around the trees (fine!), then cock its leg and begin urinating over the trees. Some poor tree collector guy will be along to retrieve these trees, perhaps he is wearing gloves, perhaps not - even if he is, I doubt he'll take them off between pick-ups, meaning he'll be transferring dog piss on the steering wheel.
Or is it no big deal, and the trees may have squirrel pee on them anyway and he'll know it's a dirty job?
YANBU - it's gross and thoughtless
YABU - meh, don't care