Until they expose an elite player (multiple grand slam winner), such as Fed/Rafa/Nole etc., it just shows that it is far from easy to cheat in tennis if you are constantly under the microscope. This is especially true now where we have zero privacy.
First of all they are not constantly under the microscope. It has been demonstrated many times in this thread and other threads that testing is a lot weaker in tennis that most other sports and there are many holes in the system.
The moment Fed/Nole/Murray/Rafa start taking performance enhancing drugs/cheating, rumors would spread like a plague and they'd have nowhere to hide.
You are making statements based purely on conjecture. How do you know that rumours would spread? How do you know it would be difficult to hide? All we know as facts are that the testing regime is weak and that players have an incentive to dope. That would strongly suggest that any player who wanted to dope wouldn't have too much difficultly.
Basically, until we have a concrete proof (such as Armstrong in cycling), it is extremely cynical to assume that the same is true in tennis at the very top of the game.
Like I said before, unless you are into conspiracy theories, it is extremely difficult to believe that the elite players, who are constantly under the microscope, and who have so much at stake, are taking performance enhancing drugs. Lower ranked guys, maybe, as they have less to lose and as they are off the spotlight, but the top 4-5...forget it.
You've misrepresented my argument and ignored the initial point you made yourself. We are not talking about if players are doping or not. We are talking about how easy it would be to dope. You initially said it would be very difficult for a top player to dope. The facts suggest otherwise.
As for whether they are actually doping, thank god you're not in charge of anything with this mentality! According to you until someone is caught it's not a problem?! The reality is:
1) doping is relatively easy to do without getting caught in tennis
2) players have an incentive to dope
3) many high level sports have doping problems.
When you take those three facts into account it is perfectly reasonable to suggest that doping may be a problem in tennis. The abusrd view is to assume that the sport is completely clean because no one has been caught by an system which is clearly inadequate.