It was not just the spying.
The four Russian officials who were arrested in Georgia were plotting to assassinate senior members of the Georgian government. To destabilize the country and close the only way for the West to get access to the Central Asian and Caspian oilfields that does not go through Russia, China or Iran.
These are terrifyingly high stakes. As Edward Lucas says in his article- the fall of this "faraway country of which we know nothing" would allow the KGB-led government of Russia to have complete control over the European energy market. Given the practice of Russia to be extremely aggressive in the use of energy as a political lever, this must not be allowed to happen.
Russia is a rogue power- and one that has not abandoned Soviet Imperial dreams. By being blind to the danger, the West could lose the new cold war without a shot being fired.
Yet another reason for the UK to reduce our use of fossil fuels as quickly as possible- as if the natural balance of the Planet was not sufficient reason.