At what point can you counter sue because this is malicious.
@Emperor Tippy your thoughts?
Not a lawyer, so...
Generally, you can sue anyone for anything in the US (seriously, you could file a lawsuit against God because your dick is too small); the court just tends to toss that kind of thing and get annoyed at you for wasting the courts time.
More seriously, it would depend on state and federal law if a cause of action exists that would get a judge to even entertain the claim. In this case, you could probably find one that would pass the smell test for a civil claim (essentially anything that harms your business would meet that standard). The real difficulty would be proving that it was actually malicious.
I mean if you have the person on tape admitting that they created the situation and filed the lawsuit solely because they want to waste your time/money/punish you then you have a decent chance of winning. But absent that, the strong presumption is going to be against the lawsuit being malicious generally speaking.