Why not? If they're not complying with court mandated orders, then the court is empowered to enact any legal (in Brasil) measures to coerce cooperation out of the offender. If whatsapp wants to operate there they have to follow the law; they stopped following the law, they're no longer welcome.
Whatsapp seems to be in a position that it could retaliate against this Brazilian judge by giving false testimony. Afterall, Whatsapp and the parties to the messages are probably the only people who know what was said in those messages; Whatsapp could modify the messages such that they exonerate the accused. If the judge has played his only trump card by blocking usage of Whatsapp in Brazil, then Whatsapp knows the absolute worst that can happen by lying about what was said in the messages. Worse, the Judge may not even be able to prove what the messages actually contained.
Oh really? What else are you supposed to do when a startup flush with cash decides to ignore the laws of your nation, exactly?
If my website gets ruled to turn over logs by some local jurisdiction in Brazil. Why should I feel compelled to comply? I am not Brazilian and I have no Brazilian business presence. It's the Internet... to be policed by every local jurisdiction in the world is ridiculous.
You mean suspected criminals, right?
It still seems pretty reactionary. The solution isn't to block an entire service.