People have the right to do whatever they wish using their money and teams are privately owned property so it really isn't a matter of ethical validity as it is a matter of personal decisions. What I think on the matter doesn't matter because if we acknowledge the team as property it isn't particularly for anyone to decide but the owner.
When an athlete plays professionally he understands that he is morally obligated to not cheat. Putting himself above the sport is not acceptable. Athletes are mostly honorable people and deserve their pay, but the salaries athletes are paid are enormous sums of money. That huge amount of money is not deserved by people who cheat to get it.