It makes no sense to insist that aliens would think as you think they should. That doesn't even make sense for humans in most cases.
> You can't hide either, the signals are already out there, they know where you are.
That's arguably not true.
We are on the cusp of being able to detect the biological markers of life on distant worlds by spectroscopy. An alien civilization that can traverse the enormous gulf between solar systems can very easily build widely spaced telescopes that can monitor all nearby solar systems for changes to atmospheric composition. Anybody who is paranoid enough to need to kill any life around them would obviously build such an array. There is no hiding from them, the technology is much too simple compared to what you need to travel between solar systems.
Maybe they can't themselves, but don't like the idea that someone else eventually may be able to.
I think you're overconfident of the safety of actively advertising our presence to the universe because you're making a lot of assumptions and only considering a small number of possibilities. The problem is that there are so many unknowns and so many shades between different possibilities that no one can really be confident about anything, except that the risk could be anywhere between zero and the maximum.
Plus, it doesn't even make sense to try to "protect" yourself because their first move if they even thought like this would be to nuke everything flat with no warning. There's no defense against it. You can't hide either, the signals are already out there, they know where you are.