*Disclaimer* I did not read the article. (Anyone surprised) By claiming that their 4th amendment rights were violated, they basically just pled guilty. The proper defense is "ZOMG some sicko hacked my WiFi!"
Not at all. There are plenty of circumstances where a 4th Amendment challenge may exist in addition to other legal and factual defenses. For example, let's say you are driving a convertible and get pulled over by the police for no good reason, and they proceed to search your car without probable cause and find a baggie of drugs in the back seat. You have two 4th Amendment challenges here - both to the stop, and also to the search. You also have a defense that the baggie in the back seat of a convertible may not have been yours, since anyone could have dropped it in there. Challenging a search on constitutional grounds is not an admission of anything.