That sounds like a fishing expedition to me.
I don't know what the law is in Sweden, but in the US there are 4th amendment protections against that sort of thing.
All evidence is admissible in court no matter how it was obtained, legally or illegally.
Of course if you can prove that the evidence was obtained illegally you can file charges for that, but the evidence will still be used.
However, the court alone decides the value of the evidence presented, and thus the weight it places in such evidence.
Obviously statements from people suspected to be coerced in some way is not considered high-value evidence.
However just because evidence is admissible doesn't mean it has to be taken into consideration. Often the court will decide that certain evidence won't be taken into consideration due to how it was obtained. This is an entirely separate decision than whether or not it should be admissible.
http://www.sfbg.com/entry.php?entry_id=9462
"Police seize DJs' laptops New police chief apparently condones policy that critics call illegal and punitive"
If that's true, than the warrant would have been limited in scope. Clearly it wasn't since the police seized everything. You can be sure there's a larger agenda than busting underage drinkers.
My Swedish is a little rusty, but from what I read in the media and the police press announcement, the following happened:
The Malmo hackerspace is located in a building that has roots in the squatter/anarchist collective scene. That group was organizing a party there where they were apparently selling alcohol without a proper license.
During the raid of that party, the police simply went through the whole building. Including the hacker space.
If this is what happened then the raid had probably completely nothing to do with the hackerspace and everything with their hosts.