Some fans just got totally frustrated with Michael's dominance and are filled with gruge so much that they aren't able to see past that.
Commentators like DC, Brundle, Herbert and Jordan are also frustrated because Schumacher kicked there butts a million times on live TV...
It's sad but it's true. You can also see it with Vettel a little bit, a lot of people don't like him and his finger either.
And I would offer the opinion that some fans can't see past the fact that Schumacher is no longer hot property. He's one of the most error ridden driver in F1 in 2011/12. Ther is a log jam of younger drivers waiting to move up and Michael's front line career is over, period. I'm only being kind by saying he should retire immediately. It would be unkind to want to see him potter on in an even worse team that Mercedes and end up scratching just to get any points.
Ferrari will want to get someone who can win in the second car and that will be no easy thing based on F2012's speed.
Your talk of Brundle, Herbert and Jordan is pure BS. Everyone knows that Michael used to demand (like Senna) ring-fenced number one territory, used to take out a driver who was a threat, used to deliberately red flag qualifying, get in the way of opponents trying to qualify etc etc. Hardly surprising these guys and many others like Warwick would state the truth.
Winning relentlessly as you say does have a negative effect but Michael bought much of his unpopularity with his actions and his fans draw their share of scorn for defence of the indefensible.