There are many words that have both general and specific uses. For example, look at the word “discussion”: we can use it as a general, non-countable word in a sentence like, “There has been much discussion about the new project.” Or, we can use it to talk about a specific speech act: “We had a discussion about the project yesterday.” In this case, “a discussion” means we talked about a few particular topics related to the project. The same is true in your question about “confrontation.” In general, it means the practice of disagreeing, arguing, fighting, etc., and so someone might say s/he “dislikes confrontation.” In the specific use, it means that there was a particular disagreement, argument, fight, etc., on a particular topic at a particular time. This makes it countable, because we’re not referring to the idea of confrontation, but to an example of it.

To "confront" someone is to tell sort something out that needed to be dealt with and to come face to face with a negative situation. Eg "I confronted her for her rude behaviour towards the teacher in class". To "avoid confrontation" is to make sure not to encounter an argument or not be told off for something you may have done that was disliked. Therefore to dislike confrontation is to dislike being told off or being put in your place.