Robert Comsol wrote:
In simpler language: Benevolent aliens would cherish the Prime Directive on our behalf, evil ones would come and say "hello"...
The so-called "evil" aliens might be making a first contact, too. There's a first time for everything, including mistakes. (And as the old adage goes, "Experience is what many people call their mistakes.") They may have a race history with no precedents of disaster between tribes, nations, etc.
And why must the Prime Directive be altruistic? Suppose the more technically advanced race has learned not to reap first contacts until a new race is ready to contribute in some way. In human dealings, I'd more readily trust mutual interest than alleged altruism. ("The road to Hell is paved with Prime Directives.")