Vinegar will not damage the paint.
Fairy liquid will not damage the paint.
BUT it can create the environment where over time the paint gets damaged by other causes.
The problem is that paint needs a wax or sealant to protect it from UV which can then cause oxidation. Acid rain which is far weaker than vinegar will slowly remove wax and can then make the car prone to oxidation. Fairy liquid removes most waxes and sealant and acid will do the same. We use vinegar extensively around the house for cleaning as it is excellent for glass and bathrooms and at times I use it on the car.
Oxidation can be seen particularly on red cars where the paint looses the shine. Even with clear coats these can oxidise and go murky.
As I mentioned some people will wash a car in acid to remove some contaminents but you do need to re-wax or seal.
So "television" you are correct - Vinegar will not damage your car.
BUT it can create conditions that mean your car can get damaged.
(It is all about the right product for the right environment - I for one would not put Autoglym on my fish and chips as this will damage you! but I have never heard of anyone getting damaged by putting Autoglym on a car but at the same time vinegar on a car is a bit like Autoglym on fish and chips
)
I had my car polished by the dealer with show room wax this looks great but offers very little protection. A bird dumped on my bonnet and it blistered the paint in less than a day. The reason was all my sealant had been removed as some bodywork had been done on the vehicle. Their wax had not damaged the car but had created conditions where it could be damaged. I always use a good quality sealant but sometimes put show room wax over this if I want to show off. Now if a bird dumps on the car I am generally safe for a couple of days (not that I leave it that long)
Some high quality sealants or waxes may not be removed by vinegar but for the sake of a couple of minutes re-applying a wax or sealant and using rubber protector or conditioner on the area you have treated with vinegar it will keep your car super shiney and also probably stop moss growing in the first place as the muck it needs to grow on can not stick.
With regards to rubbing - Also it depends what you rub the paint with i.e. the cloth. Rubbing could cause abrassion of the paint but if you used a high quality microfibre or terry towl it probably would do nothing. But if you used a dish cloth it may. I have rubbed my car with vinegar, T Cut, tar remover etc but I try to use an appropriate cloth.