You are correct. Bird droppings react violently with the chemical composition of the paint, thereby proving extremely detrimental to the painted surface.
What irritates me to the extent of pulling my hair out is this:
Spend the entire Sunday cleaning and polishing the car. Clean the windscreen and polish it till it glitters like a diamond. Take the car out and enjoy jealous looks of the people towards your gleaming car. And suddenly, POOP. There it is, seemingly out of nowhere,right in front of your eyes, on your hitherto glittering windscreen, shining like a beacon in the middle of a calm sea, and as visible to everyone as a buffalo in a pack of cows - a spoonful of some bird's last night's dinner.