No there is no problem against the patent troll for suing people. The person being sued has no recourse.

With the patent system you are guilty until you prove yourself innocent. The burden of proof, in practice, is absurdly low. The reason for this is that most people cave in with a lawyer’s letter since the vast majority of the time. They do this because it’s cheaper to pay licensing fees then to fight a patent claim and win. The total cost of the burden of the defense is on the person being sued. There is no recourse for compensation.

Smart lawyers who own patents (aka patent trolls) do not produce any produce or service, so it’s impossible for them to be sued back. If they do nothing but sue other people then they are completely free of any danger of being counter sued due to patent infringement. Accordingly they will price their licensing fees to be slightly cheaper then fighting them and winning against them. It’s stupid to fight them oftentimes because they know the cost of litigation and base their licensing fees on this.

If you do spend your money defeating the patents, then you just did your competitors a favor. Since they do not share your cost of defense and they are free from licensing fees due to you defeating the patent troll then they are given a significant competitive advantage. Many companies who have proof that the patents are invalid will often sit on this knowledge for this very reason.