I've lived in MK for 9 years now and love it. Prior to that, I've lived in: -
Oxford - beautiful, history, dreaming spires blahblah, but absolutely fucking awful traffic, and forget parking anywhere near the centre.
London (zone 2, SE) - nice enough, fun as a young adult with decent income, great access to all sorts of cultural things, but after we moved out, our landlord sold our 2 bed flat for 200K more than we paid for our 4 bed house in MK.
Small market town in Shropshire - lovely place to raise children, idyllic, safe, but almost everyone leaves for uni and never returns.
MK doesn't have the cultural or historical clout of Oxford or London, but it is far more affordable, accessible, and functional. Has pretty much all the shops and nearly all the activities most people could want. Schools are mostly decent, traffic and parking are good, and it's well connected.
As for "made for people on housing benefit" - there are some of the older estates that were primarily council housing, but the majority of the more recent ones are nicer and mainly build for private ownership. Crime is not a particularly big problem compared with other similar sized cities, I think? My kids are a bit young to worry about county lines etc, but I don't think it's a huge deal here.
People just like to be dicks about anything remotely different.