What I gathered from your description is that the 1M owner is hugely insecure.
There is no need to put down someone else's car unless you're like that. Every car has its strengths and weaknesses. Including the 1M. If he can't recognize the strengths of the M3, then it's because he's feeling too secure.
Just my two cents, but I actually would not want to keep talking with that guy... There are enough enthusiasts who can appreciate a variety of cars (including from different brands) while still being honest and balanced.
Present: 2013 M3 coupe (Azurite Black, Black, Piano Black)
Past: 2010 335i coupe (Monaco Blue, Cream Beige, Grey Poplar)
+ miata nut (2004 GT/LS and 2013 GS/Club Edition)