Confidence is highly different from arrogance
Arrogance is unattractive
Annoying
Pompous
Pressumptuous
More often than not, with very little (whatever they are arrogant about) to back it up
It's tedious
It's also highly repetitive, you can often predict what they will say when certain topics are brpught up
Can lead to them being highly rude and making more insulting comments than msot people would dare (due to an inflated confidence, and them always being right)
Argumentative (I like someone being argumentative. but there is argumentative and argumentative)
Maybe this is me being bias, and I am sure that it will be fired back at me that I am generalising, but I'm basing this one an (ex) friend of mine, and the points I have made are logistical, I believe
I think the main reason people don't like it is because it belittles them though