It's a tough call. Go further left, appeal to more people and solidify the base but in doing so...push the country to a more extreme level of division.
I agree entirely with the 2nd paragraph, the third paragraph I think incorrectly assigns victory for Corbyn while ignoring the massive failure of May, right on with paragraph 4, and the last paragraph is the tough one. That caution is really what's keeping us together right now.
I watched this speech online - he's a good orator when he's passionate.