In the spirit of further contrarianism, I'll note that although your points are all valid, they do not really save the message of "The Bottom Line" post, unless you start interpreting the message in a rather liberal way instead of taking it literally, and this is undesirable under commonly held LW values.
[For example, atheists usually balk when people start interpreting the bible left and right, keeping the desirable conclusions and throwing away the rest, etc.]
No, it's functionally identical to the original analogy. Rationalists make it easy to change their bottom line as new evidence comes in, so their bottom line isn't fixed forever at the start.
For example, I recently scrapped a post because I found out that the anecdote I was going to start with wasn't what I thought it was at all, which raised my estimate that I was oversimplifying the rest of it. Yeah, I started with an idea of what I wanted to write, but when I learned new things I changed my confidence in that idea.
In the spirit of contrarianism, I'd like to argue against The Bottom Line.
As I understand the post, its idea is that a rationalist should never "start with a bottom line and then fill out the arguments".
It sounds neat, but I think it is not psychologically feasible. I find that whenever I actually argue, I always have the conclusion already written. Without it, it is impossible to have any direction, and an argument without any direction does not go anywhere.
What actually happens is:
It is at the point 3 that the biases really struck. Motivated Stopping makes me stop checking too early, and Motivated Continuation makes me look for better arguments when defective ones are found for the conclusion I seek, but not for alternatives, resulting in Straw Men.