He's been really naive to think he could do this to appear tough. If the cabinet announced a wealth tax at the same time then maybe, maybe, the kick back among Labour members and MPs wouldn't have been so strong. He's expounded a lot of political capital over a measure that wasn't in the manifesto and few in the party would've supported campaigning on.
The result: members have resigned, the TUC speech was a damp squib, a cohort of MPs are bitter about having to file through the lobby, MP inboxes are full, and CLPs are now infighting. It's just a bit dumb. Really dumb.