Probably 'cause we are the best.
But seriously, i think they regard Sonic fans the worst because they cant take them down easily.
You should see League of Legends community, most people that say Call of Duty or sonic communities are the worst have probably NEVER played LoL. Even Witcher community are worse XD
Lastly, from the thread the OP linked i loled so hard. People must have been scarred real bad by the so called "sonic community" to have regarded them as the worst, where did they even find this "sonic community" lol