'Hated' and 'maligned' aren't the same thing -- and besides, I'd suggest that 'least liked' is more accurate than 'hated'.
For 'least liked' the M5 has to win hands down. A conspiracy theory of 'Pseudo Experts' holds no water at all: why is it in the interests of a 'Pseudo Expert' (or anyone else) to talk it down?
The simple truth is that it just didn't sell, and those who remember its introduction -- I still have the pamphlet somewhere -- were not particularly surprised. Since its discontinuation it has acquired a number of fierce devotees, but hey, so have Trabants.
For 'maligned' -- in other words, 'attacked unjustly' (usually by those who hadn't tried it) -- the M8 must surely be the winner.
Cheers,
R.