> I think my idea of holding your own patent was not for the ability to counter-sue, but (and I am quite obviously not a lawyer) so you have a legal basis to petition for dismissal of the patent troll's suit.

What, exactly is this "basis"?

Note that a given thing can be covered by multiple patents, owned by different people.

Yes, patents can be prior art against other patents, but you don't need to own a patent to use it as prior art.