I see no mention of this in that article, did you guys hear the judges words for yourselves or just permitting yourselves to define the situation as you saw it?
Until proven otherwise in the future, there was no charges of assault or battery.
So no, it was an excessive "sentence."
http://www.guardian.co.uk/uk/2011/aug/02/protester-jailed-throwing-pie-murdoch
He admitted assault.
May-Bowles, of Windsor, in Berkshire, admitted assault and causing harassment, alarm or distress at a hearing on Friday.