Your question got me thinking about this for a minute! The reason that it is indirect is because the author's conclusion is that the 40% fare increase must be implemented, but it never uses any positive reasoning for the fare increase, but rather only provides reasons for why not increasing the fare by 40% would be detrimental.
An example using similar reasoning:
We must go the park today. Staying inside all day would be a waste. Doing anything other than going to the park would be a bad use of our day.
Here, again, we are supporting the conclusion indirectly because we have not provided a single reason for going to the park other than not going would be bad.
I hope this helps. Please let me know if you have any other questions.