People who don't like Zoro are always something to me. Don't know what you could say bad about him. Yes his fans might be so arrogant ... But Zoro the character ? Just a common man without any lineage (at least for now) who trains everyday to became the strongest, loyal to his crew and his captain, ready to give away his life or pride for someone else, who never forget to respect any good characters, doesn't annoy you by his acts, doesn't do any irritating face/behaviour.
He is just calm and talk when it needs but some people hate that and call it "one dimensional" because he is the "badass" character of the manga but they love katakuri, shanks, whitebeard for the same reason. We know friends or family or someone who is calm and serious, would you call them also one dimensional human ? No of course, it's not a bad thing to be serious but what to do, people want zoro to act like others characters but they hate at the same time when characters are noisy, too emotional.
You basically just want to hate someone, just admit it ...
I don't hate any characters in OP beside Spandam/Charlos, some fanbase are dumb but i wouldn't change my mind about a character because of that.