Given that the US is not a signatory to several international treaties and regularly employs solitary confinement, which is internationally considered as a form of torture, there is a humanitarian argument against the extradition. The desire to comply with the extradition request seems to be more about politics (i.e. maintaining good relationships with the US) than the rule of law.

The treatment of Manning should be sufficient evidence to deny the claim that Assange would receive a fair trial and treatment as a prisoner that is compatible with human rights (i.e. that excludes torture). But given that the judgement argues that even the plans to assassinate him were justified, I doubt this will be given any consideration.