There is an old saying "If you can't do the time, don't do the crime."
Graffiti "artists" (very few with an aerosol paint can and time on their hands can be described as having any artistic talent, not even by Turner prize standards) and activists choose to commit their criminal activity in the full knowledge of the possible consequences and if they continue on their chosen path then they are implicitly accepting that they will have to endure those consequences.
Not given in the article is any idea of the previous criminal history of these two "artists". One suspects that instead of the short lived short sharp shock approach we would find the usual hundreds of previous arrests and prosecutions, social services reports, cautions and fines galore and all the usual community service orders ... and all to no avail as the behaviour continues and is reinforced by the leniency shown them previously. Poor journalism not to investigate and report such and one suspects an activist journalist at work here with little regard for true journalism. Incidentally, no previous hsitory for the Nelson's column criminals either.
However, while many of us find graffiti deserving, ultimately, of severe penalties, we are unlikely to get too worked up about the punishments handed out to them.
But there is another dimension. Graffiti artists often are loners without a cause.
Climate activists are backed by Greenpeace, friends of the earth etc who all have significant funds (partly funded by you and me via the UK Government and the EU) and a sympathetic media with the likes of Geoff Lean, Georgie Moonbat etc. ready to print whatever press handouts are given to them as "news" and equally ready to inflate any kind of significant penalty into a cause celebre.
Any kind of fitting penalty and we'd never hear the end of it about how these "brave and courageous people have paid a heavy penalty for their cause and made a great sacrifice (though the fines would be paid by the NGO's and used as an excuse for more fund raising with a plea for public donations to help out....).
Graffiti artists do not have this sort of backing and it is "safe" to come down on them heavily.
While the motivation of the judges is rightly questioned and does indeed cause concern, especially about the disproportionate responses between different types of crime (including the police and CPS responses), these "slap on the wrist punishments make it very difficult for the NGO's and activists to generate any kind of heat. They can hardly take the case all the way to the ECHR on the basis of a £30 fine nor find some publicity seeking MPs ready to ask questions in the house.
When all they can point to is a paltry £30 fine the putting of anti-smog masks on statues becomes pretty much a pointless childish prank which possibly does more harm than good to their cause and especially where the costs are born by the tax payer.
Fortunately the biased judges haven't twigged that the best thing they can do for their personal commitment to AGW would be to hand out £30 fines and a complimentary set of permanent markers to graffiti artists and death sentences or rendition to Guantanamo Bay as Terrorists for AGW activists (tough even so some of the public might applaud such sentences, more than might be thought, perhaps.)