Depends what you mean by cheating. Prior to 1998 doping was the norm, and had been since the sport began and inhuman distances were commonplace in cycle races. People who doped were breaking the rules, but they were not cheating anyone. Everyone was at it, so all the likes of simpson did was to ensure they were playing on a level field.
In '98 the lid came off, and the reputation of the sport was badly damaged. The extent of doping became known and the public would not accept what they saw. The UCI tried to clean it up, but instead of complying the riders just became cleverer at fooling the testers. The crime then became more serious, because they knew what they were doing would hurt the sport badly, and that the products they were using was putting their lives at risk.
After Puerto and the massive headlines last years tour generated, doping became seriously bad news, putting the future of professional cycling in serious danger. Those who still carried on after that, in the face of attempts by not only the UCI but their peers were not only cheats, but out and out crooks. They were no longer merely being one of the boys, but were knowingly and cynically cheating their fellow riders and the fans of the sport.
So whether your heros were cheats or not depends in which era they rode. Remember that most of the footballers who won the World Cup for England would be classed as violent thugs if they played the same way in todays game. The rules change with time.