These days there are companies/individuals who will fund your patent defense costs for a percentage of the patent rights.
The patent system is kind of screwed up for the same reason the rest of the litigation process usually sucks. If they had loser pays legal fees most of this kind of behavior would go away as if you have a valuable patent finding the front money to prosecute patent infringement would be a lot easier.
Similar results would be seen in the rest of the non criminal legal system and I wouldn't have had to peel off endless warning labels on the ladder I just bought.
Trial lawyers might actually be encouraged to do something useful.