I don't see how opening it makes it safer. It's very different from security things, where some "white hat" can find a security, and they can then fix it so instances don't get hacked. Sure, a bad person could run the software without fixing the bug, but that isn't going to harm anyone but themselves.
That isn't the case here. If some well meaning person discovers a way that you can create a pandemic causing superbug, they can't just "fix" the AI to make that impossible. Not if it is open source. Very different thing.