A University professor who would put a sign on his door saying "Away Fighting The Forces of Capitalism" when he was out of office once told me that the reason populism tends to pool around reactionary right-wing ideas is that the motivations for, and expected benefits of left-wing ideologies are less easily quantifiable and thus harder to express.
The people who like to portray Labour as living in cloud-cuckoo land are the sort of people who'd take a financial hit from a Labour administration. They're some of the richest people in the country, and they're squealing at the thought of seeing some of their advantages go swirling down the plughole.
Both the Labour Party and the Liberal Democrats will go into the May 2015 general election on the basis that, if elected, they will introduce a Mansion Tax. David Cameron has ruled this out - but unless the Conservative Party wins an overall majority it is likely that some form of the policy will be introduced in the next few years.