You are grasping for straws. No one said open source is perfect. But it's just an obvious fact that open source is going to be easier to audit than closed source.
But isn't that their point? In the age of AI, maybe being "easier to audit" is as much a risk than an assurance? I'm not sure I agree, but it is interesting to mull over. Further, either way, your tone and response is not very charitable, to say the least. From the outside, you are the only one blustering and grasping here. Not everything needs to be so antagonistic maybe?
Reverse uno. The same AI can be used to fix the holes in the open source code. And a LOT more AI review by benevolent parties is gonna hit that open source code than the closed source.