https://readallcomics.com/invincible-029-2006/ this is where I read it online

I think it would be pretty far fetched to think that some random Earthling would read one of his crappy SF novels then go looking for the invincible gun or whatever to kill the Viltrumites with it. They don’t even know the Viltrumites exist when Nolan shows up, and there’s nothing to connect Omni-Man to his writing career.

All you have to do is think of the presented alternatives, which are: kill the guy, or lock him up and throw away the key. So yeah, this is better. Mark is being juvenile and his whole arc makes that painfully clear.