(Good Manager + No Tech Skills) > (Bad manager + great tech skills).
I don't think that is the argument... I think it is:
(Good Manager + No Tech Skill) < (Good Manager + great tech skills)...
and on that point no one would disagree.
It is interesting how so many have tried to frame the argument the first way - perhaps they are more of a unicorn than one would hope... but it would still be better to have BOTH skills.
Usually what happens is the best coder in the bunch gets asked to manage the team but 1) doesn't know anything about management and 2) doesn't want to be a manager but likes the power and fancy title. So this person just keeps on coding but with less accountability to the other team members.
What the tech world needs is more skilled managers, not more technical managers. People overvalue the notion of calling developers' bluff because there is a basic level of trust that is missing.