Is there really no such thing as bad publicity?

One thing that I've never quite understood is the famous saying "there's no such thing as bad publicity". there is nowhere that explains where the quote originated from apart from that it is commonly associated with P.T Barnum. However there is no proof that he even spoke those words. Brendan Behen an Irish author and dramatist comically added to the phrase saaying "there's no such thing as bad publicity except your own arbituary". But what does the phrase actually mean in a world of advertising?
as we know, we are bombarded with thousands of commercials daily and the companies and agencies thrive to create brilliant and different advertising in order to promote whatever it is they are trying to sell. this is the same for individuals trying to give themselves a particular image, most of the time, a good one.
so how can publicity be good if it is bad?
Succes de scandale, french for success from scandal, might sound contradictory but means scandal causes attention which whether good or bad leads to fame or other such success.
however, bad publicity can have a negative effect on a company, it can damage a brands name and could even be permanent. some can have no effect or maybe even a positive one.
bad publicity brings exposure to a brand/person/ which is a good thing but in the case of advertising a bad advert isnt necesarilly going to make anyone buy the product and in some cases it may make people avoid the brand altogether. in the case of a person lets say someone trying to become president, bad publicity is definately not going to be to positive with the public. unless of course you already love that person/brand/ product etc.

my conclusion is that bad publicity does exist but whether it has a negative effect, most of the time, probably not, maybe a little bit..

Pepsi's one calorie print ads (germany)