Understand your point, as of course the same critique "doesn't represent everybody" can be applied to absolutely any medium.
As an example, Goodison Park reflects it's customers, not all Evertonians.
To add, that's 28,000 active accounts (register/login/posts). More people will visit GOT in the next 10 minutes, than will be at Selhurst Park on Wednesday and inside a few hours, more will visit than will be at Goodison on Saturday.
Add to the 250,000 fans following GOT on social - we've never used our different comms to encourage votes on the manager. However, using our social CRM tool we can track all inbound messaging and from the last 100k interactions on social containing 'Martinez/Manager' there is a 92% negative sentiment score.