Has it occurred to nobody that if JSO kept on causing massive disruption and getting away with it, other protest groups might become emboldened? Suppose there was a "stop the boats" movement that blockaded the M25? Would they have the same sympathy as JSO? Remember the pressure group Fathers for Justice, who did similar "heroic" antics by dressing as Spiderman, and scaling cranes, bridges and the like, forcing roads to be closed? Would they have the hero's reception "their cause is so worthy, they're entitled to peaceful protest!" that JSO seem to have? Would we still be OK with one protest group after another upping the ante, until there is complete anarchy? Remember the London riots: they started with anger about a young man dying in police custody, but then escalated at alarming speed. More and more people joined in, knowing that they could easily outnumber the "feds" (their word, not mine), perhaps thinking they would get away with it, under our soft-touch justice system. The courts worked overtime to prosecute the rioters; and incidentally, a very few of them were moneyed and middle class, who were copycats of what was going on around them.
And this is the danger: copycat protests. There has to be a deterrent. Sooner or later, the line had to be drawn, and a message had to be sent "if you disrupt like this, you will be locked up"; JSO kept on causing mayhem again and again, there had to come a point when "enough is enough!", with the book thrown at them (I love that phrase), otherwise, other groups might believe themselves to be similarly invincible. They were getting away with it again, and again, and again, and I'm really surprised that so far, nobody took matters into their own hands, and drove straight through them and killed them (and such a driver would probably receive a much longer sentence than dear Cressie). Although peaceful protest is acceptable, systematically causing mayhem is not, and is very far from "peaceful". The line on acceptable protest has to be drawn somewhere.
That's not to say that the government is fair and impartial about who they lock up: let's suppose that an anti-lockdown movement had scaled the gantries instead. They would probably have been remanded at once, and given much longer sentences before their feet even touched the ground.