You cannot blame schumi for the fuel tampering or TC issues at Benetton. I think he can take a little of the blame for Hill, but in that split second he was just protecting his line into the corner - at that point it wouldn't be clear if he could continue. Hill is also to blame by making a silly move in the heat of the moment and diving up the inside.
As for Villeneuve, again Schumi can hold some of the blame for closing the door big time, but bear in mind Villeneuve came from miles back to do the pass. It can't have been pre-meditated. I bet in similar situations almost all the champions of the last 30 years would have had a go at defending their position just as forcibly.
Alonso hasn't been in F1 long enough to have shown his determination. His first championship was easy, as his only competition was a McLaren that couldn't finish races, although he did prove he can race. He had no need to do nasty things, and no real opportunity. But we've seen in the last few races that Alonso does get rattled, and does do some nasty things, so maybe it's only a matter of time.
In 94 remember the FIA was against Michael (and his team), and every decision favoured Hill and Williams. Yet no one remembers that now. In 97 there were less technical politics going on, and Schumi made a car that shouldn't have been anywhere near the front nearly snatch the title.
There is no doubting Schumi's brilliance behind the wheel, and he's only had a few black marks to his name. But no more that any of the other greats really.