Because this complicates the issue - not only are they just here illegally, they're taking actions to make their illegalness less taboo.
As far as I can tell in the article, what they're taking action against is a perceived illegal arrest. If a person was not in the country illegally, you would have no problem with that person fighting an illegal arrest.
Like I said, at the heart of things, your real problem is with their illegal residence within the country, not anything else. Why not just make arguments about why their illegal residence within the country shouldn't be tolerated? It'd be more effective than posting a new topic every single time an illegal immigrant does something.