I would have to say the beginning of the Attitude era was the Raw where the WWF title changed hands for the first time on the show. It was right after the PPV where Bret Hart won the title in a fatal four way just to lose it to Sid the next night because of interference by Steve Austin. That sparked the bitterness in Bret Hart which turned him heel. He started showing it when HBK forfeit the title (in Bret's eyes because HBK was afraid of him) and then you had Austin being a thorn in his side and it all snapped that night. Fans saw Bret as a whiner, Stone Cold used that to get over, DX was basically formed to mock it and now since Bret was a bad guy, still standing for rightousness in his eyes, fans were against and cheered for the people of the opposite. Stone Cold and DX which had the snowball down a hill effect after that.