AVG also detects your cracks and keygens for your pirated software, whats new?
That's because cracks and keygens are trojans, more often than not.
They do it on purpose. I read once the article from antivirus company where they mentioned they remove certain keygens, because they target the other software that company sells. Makes sense. And if they protect themselves that way, they could protect others too, if some other company will ask nicely.