Of course, the reason this is being done, and done now, is (
IMHO) entirely political. It's to appeal to grass-roots Labour, the core vote. It's to appeal to the social engineers in the party that want to bleed the rich, and it's designed to
appear to do that. In other words, it's naked political opportunism and electioneering, and it's designed to allow Brown to pose as the "socialist" that's addressing inequality, while he prattles on about the Tory's inheritance tax policy, ignoring the fact that as Chancellor, Brown could have down this and any number of other things to address social inequality over 13 years, and instead, abolished the 10% tax band.
So, while I'm incredibly cynical about why they're doing this and doing it now, I still think that in the circumstances, there's nothing at all wrong with doing it.