We're going to have to agree to disagree on this one.
What happened in the past is perfectly relevant.
Many drivers have done questionable things in order to gain an advantage over their rivals, which are "gentlemanly".
Recently, I would look towards 2009, when Hamilton lied in Australia (I think it was), in order to gain a few extra points and get another driver (Trulli, I think it was), disqualified from the race.
Go back to 2007, Hamilton broke team orders during Hungarian qualifying, to gain an advantage over Alonso. Alonso responded by holding Hamilton up in the pits, to prevent him from having a final qualifying run.
Go back to the Scumacher years - he had no qualms about taking people off the track, if it meant he could win the title. Furthermore, in Monaco 2006 (I think it was), he parked his car across the racing line to ensure nobody could go faster than him. MSc got up to many tricks during his career and this was not long ago.
Go back further in time and you will see Senna, who would think nothing of taking other people off the track, if only to teach them a lesson or make a point.
I have absolutely no doubt that Alonso, Vettel and Hamilton, will get up to "tricks" during the next few years. This won't change. The Stewards are much stricter than they have been in the past, however, to this end, drivers have become smarter and found new ways of gaining an advantage.
The only difference between 1990 and 2010 is that in 1990, drivers performed their tricks in a more obvious manner. In 2010+, drivers are more discreet.
The ethics (if that is indeed the word you mean to use), have not changed one bit. To win at all costs always has and continues to be, the aim of top drivers (perhaps Button, excluded).