An entirely knee-jerk reaction to a freak one off event. What next, am I not allowed to drive my car alone in case I fall asleep at the wheel?
Complete straw man analogy, as I would hope you know. Air travel is subject to rather stricter regulation that car travel, amongst other reasons because if planes crashed as often as cars, no-one would ever get on a plane, and then you wouldn't have a job. You also don't have direct responsibilty for up to 600 people's lives in your car.
This has really upset some pilot's egos hasn't it? Most crashes are 'freak one off events', do you suggest we should just carry on then, no investigations, no ADs, no attempts to improve safety? In any case, it is not a freak one off event, in recent years pilot suicide crashes are probably a statistically significant proportion of crashes. And the preference has been to do so when alone in the cockpit. There are perfectly good reasons - psychological and practical - that a person is less likely to follow through on their intentions if they are not alone. Therefore an extra person in the cockpit serves two useful purposes - reducing the likelihood the individual will act, and providing someone to open the door.
Finally, would you care to tell me how many crashes have been caused by deliberate action by cabin crew, and how many by pilots. As far as I'm aware the pilots are inifitely more responsible. I've never felt comfortable with just having one person on the cockpit, for many other perfectly innocent reasons, or with inpenetrable doors. On the balance of probability, this is likely to reduce risk, and that is all the regulators are concnerned about.