If you hand someone a ton of power and they abuse it, you can expect, at the very least, the people affected by that abuse to blame you for handing it to the wrong person.

And since social media works the way it does, you can also expect a ton of unaffected people to also pick up their pitchforks and join in without having any real clue what's going on.

And that's assuming there isn't some law somewhere that really does put you on the hook for it.

300 forums is a lot of power.

It makes a lot more sense to expect the sub-admins of those forums to start their own communities elsewhere than for just hand power to a single person over all of them.