otherwise very reasonable
I haven't seen anyone being unreasonable, it's just that some disagree that 2 on the flight deck at all times with all operators is a panacea.
Depending on where you work and what you are operating it's quite conceivable and reasonable that you might see the blind enforcement of a rule requiring 2 on the flight deck at all times as possibly introducing extra risks, unless extra checks, procedures and specific training are introduced.
I think you'll find the BEA report on the Germanwing's accident said much the same - the BEA spokesperson at the press conference on the day of release of the report certainly said so.