Its going round in circles but as things stand nobody can command confidence. what you are saying is that labour should hold their nose and get behind Clarke but that Tories shouldn't do the same for Corbyn. Its just double standards.
It doesn't have to be Clarke. It has to be someone that a majority can get behind. Unless something drastic changes, that is
not Corbyn, no matter how much you wish it were.
That doesn't mean it has to be a Tory. I've mentioned Harriet Harmon several times. Margaret Beckett is another name that is being bandied about, although she'll most likely become Speaker.
I couldnt really care less who gets the extension and calls an election, do you? why should a Tory?
Corbyn, rightly or wrongly, is perceived to be incompetent and untrustworthy. That's why people care. Not because of what colour tie he wears.
Look at it this way - there's a bunch of people saying "not Corbyn", and Corbyn saying "only me". The two positions are not equivalent. One is shutting down a lot more possibilities than the other, and in a way that seems designed to personally benefit him rather than trying to do right by the country as a whole.
Part of a politician's job is making people warm to and trust you. Corbyn is not good at this. Another part of a politician's job is compromising for the good of the country. Corbyn is refusing to do this. His truculence on this matter is an example of why people don't trust him to be PM, and it's an example of why they're probably right not to - he
wouldn't act like the statesman he'd be required to and, even if he did manage to get appointed as PM, the government would likely fall apart PDQ as he tried to push through what he thought was right rather than what the majority wants and people rebel against him. A GNU would require a delicate touch, which Corbyn has not shown he possesses and, in fact, is currently demonstrating he doesn't.