There is also a difference between noting "generalities" and a prejudiced mentality hiding under the banner of speaking "truth". Every stereotype has some grain of truth to it, after all. Bigotry is always in an unjustified exaggeration that ends up presenting great lies about many people, while it tells truth only about comparatively very few people.
Also, a pattern emerges after a while, some groups always noted for negative generalities often without proof, or never good ones. There's normal irreverent banter of which many a Kenyan jokes are made, but then there's also an unnatural and imbalanced (negative) focus on some to the exclusion of others. It is soon easy to tell you are dealing with a good old bigot and not an irreverent msemakweli. Bigotry is for me a sustained negative predisposition towards members of a certain group. People from all quarters suffer from it, including the most progressive (politically), but it should not be confused with crude ukweli which does not pick favourites. The latter may be a jerk, but the former is a bigot.