I suppose that depends on the motivation of whoever did it.
If it was to express anger at the election result, it worked, but probably at the expense of the support of a lot of folk who may otherwise have sympathised with the scrawler.
If it was to garner anti-tory support, the action was about as appropriate as daubing "Fuck Cricket" on a statue of Mandela.
As far as misdirected anger is concerned it's pretty spectacular given that Downing Street, the MoD, the DoH, DPP and even a fucking McDonalds were all within spitting distance!