Actually, you *did* willingly install it, you just didn't know it.
I guarantee that SOMEWHERE in the TOS that you're SUPPOSED to read when you install AIM, it has a provision for "necessary software for AIM functionality," or some bullshit like that. So you agreed to install Viewpoint.
OOPS. Shoulda read the fine print
I agree that it's a little weird, because I've never seen AIM use Viewpoint, but I don't agree that they installed it without your permission.