I know what you are saying but I disagree. The time to speak out was during the election of a leader. When the democratic process is complete you abide by it and do your best to make it work. Deliberately being disloyal to everyone you don't completely agree with is not on really. After all, if you are in Labour Party you surely must realise that sooner or later you are going to have to work with, and perhaps for, a socialist......
Mate, we had another three years of Martinez to look forward to if we followed that logic.
If a leader fails, you redress the situation and bring in someone who can actually lead.
The problem with Corbyn is that he has absolutely no chance of winning an election. When politicians see that, they're going to do something about it, because they exist to gain power and exercise that power to the benefit of their constituents. No Labour politician should be happy being a party of protest but no substance.