An example:
https://www.dailymail.co.uk/news/art...st-racist.html
The new advert for the Grinch has, on one side of the Imax cinema in Waterloo, the phrase "Welcome to South London. This is your last chance to turn around".
This has had complaints that it is racist. Quite apart from the fact that there isn't one race of South Londoners (London, south of the river, is incredibly diverse, and people from dozens of races live here), the "insult" is clearly meant as a joke. I live in Greater London (about 10 miles south of the river) and I find it mildly amusing, not offensive.
Sadly, there are increasing numbers of incidents that are actually racist, and can involve serious threats, and I think reporting stuff like this actually negatively impacts the victims of those assaults, because it means people are more likely to dismiss them.