I'm not remotely saying you are the only person saying it!
If Michael Keane missed the exact same penalty last night he would not be getting called arrogant though. He would be getting called stupid, I guess because that's the pigeon hole that he gets put in.
Honestly I would stick up for anybody taking and missing a penalty.
Onana's pen last night was not a rarity, loads of players take pens like that. I don't really get it personally as I think if you get some power on a pen there is a good chance it goes in even if the keeper reaches it, but its not down to arrogance or anything like that, its just how some players (bafflingly in my opinion) take their penalties.