His antics is not what bothers people. What really bothers them is the job he is doing at Arsenal. 'Lego Pep' was never supposed to have Arsenal beyond a team that plays attractive football and would challenge 4th spot and compete for the FA Cup, but nothing beyond that. The fact he has built the current Arsenal into what it is, bothers a lot of people.
8th, 8th, 5th, then BAM. Who knows what will happen at seasons end. But I know every rival fans now sees Arsenal, and especially Arteta in a different light.