I suppose the other explanation he posts shit like that (that is, does he do it because he is bonkers, stupid a liar or a combination of all three) is that it is simple clickbait. UA has the usual sidebar advertising, which presumably generates income for UA based on numbers of viewings. If he knows posting a load of shite about City will generate a lengthy discussion in his comments section, it all drives the advertising revenue up. That would explain why he is keen to write about City so much, when it is not otherwise easy to see why an Arsenal forum has this obsession about us.