Do you have any idea how much Assange and WikiLeaks has cooperated/collaborated with Russian agents? The US 2016 elections were a shit show in no small part due to WikiLeaks releasing only the Democrats emails. Zero Republican emails were leaked, and the most damning part of this is that the released Democrat emails were completely innocuous, but when a website called WikiLeaks releases a huge bulk of emails they've labeled as suspicious or scandalous, stupid people jump to unsupported conclusions and you end up with unqualified politicians undermining democracy, and we're not the only country this happened to. Assange and WikiLeaks are guilty of participating in Russian attempts to spread disinformation in support of the Russian's agenda at a bare minimum.
Assange might not be guilty of being the kind of traitor we traditionally think of, but he's still a dangerous individual that will help overthrow legitimate governments by misrepresenting illegal activities as exposing scandals, none of which actually exist.
So tell me again, how exactly is Julian Assange the single most hard hitting journalist of the last decade? Very little of what he claimed turned out to be accurate, and he participated in withholding information from the public which actually did have a chance of exposing serious political corruption. I might also remind you that despite essentially being a partisan shill for the Republicans (greatly helping them win in 2014 and 2016), they attempted to put him in jail as well.
The problem isn't that a lot of Democrat rank and file want to see Assange in jail, it's that way to many Republican rank and file haven't seen him for the liar and yellow journalist he his.