This is not a race or an animal for those of you who are not native English speakers this is a word that describes certain people who have a very nasty demeanor about them. They act in a mean-spirited and surly way. Maybe you know one or two? I do.
A churlish person is difficult to work or deal with and it is in their nature to try to score points against those they dislike. It often manifests itself in their verbal interaction and in their correspondence. They are unpleasant, mean and deliberately discourteous.
Here is an article from Harvard on the subject: https://hbr.org/2014/10/how-to-deal-with-a-mean-colleague.
The best advice is to realize that you should not take the blame and you can stand up to them – it is a well-known fact that churlish bullies pick targets that are highly skilled and well-liked.