From the blog posting I read yesterday, the individual was not arrested for his political convictions. He was not only a climate activist, but also a squatter. Apparently there were several police officers hurt during a legally mandated eviction of the building that he squatted.
Saying "omg they arrested a climate activist" is like saying "omg, they arrested filesystem developer Hans Reiser!"
Presumably the charge is not "resisting arrest", but "assault of an officer of the law". Several officers missed a couple of days work, one officer had to stop working for two weeks.
I haven't more on the subject, but I can certainly imagine that they started an investigation only in the days afterwards, when doctors had established reports and cooler heads prevailed.
Look at it from the perspective of the state / society. What's the alternative? Arrest everyone you find in the house, every time when you think you may press charges, and hold them indefinitely until you sort things out?
The article stated that he refused to give ID / fingerprints at the time (which is his right, as he was not charged). Clearly he no longer has a house; you just kicked him out. What do you do? How do you find him?
So they asked for an international warrant for his IP (not the contents) so that they could find him, which was approved by a disinterested third party. The warrant was executed, and now he will answer in a court of law, where he can argue his innocence while the onus is on the state to prove the contrary.
Contrast that with the alternative approach "in the heat of things" (arresting everyone, retrebutive escalating violence) and I think it's pretty amazing that our society works this way, and how much effort is spent to safeguard both justice and individual liberties. Hell, in the US, 25% of homicide-by-police is happen as the result of traffic stops that turned sour.
As far as I can tell, this was about squatting in an unused commercial space that was once a restaurant. The spot had been damaged prior to the squatting and no renovations to fix it had started.
So, yes, a crime, but comparing it to Hans Reiser seems a bit over the top.
Saying "omg they arrested a climate activist" is like saying "omg, they arrested filesystem developer Hans Reiser!"