We never let the Republicans get away with it, why should (new) Labor get a pass? Just because they are left of the Tories? The fact is whoever gets elected in the US (Clinton or Trump) you either get a hawkish interventionist at best or an unhinged and unpredictable maniac who has the potential to be a warmonger at worst. Blair and his ilk survive through the people and policies of New labor, and we don't need more war criminals in office.
If the only way to get a win is to basically become a Tory is disguise then... what exactly is the point? No doubt Corbyn will win the leadership election again, and after all, why shouldn't he? It is the will of the people, and if he does win he needed to stay. And if Smith wins, again, the people have decided and then Corbyn needed to go.