I wonder what kind of gun would you need to chase away an orca. I'm going to assume 9mm wouldn't even penetrate their thick skin and subskin fat.
Hopefully no one tries to find out. There's only 50k orcas in the world, they're more valuable than us.
Species diversity is unquestionably important. This small population of intelligent aquatic mammals is unique and beautiful and valuable. The eons of evolutionary hill climbing that led to them cannot be reproduced. They're a distillation of all that has happened to their lineage up to this point, and that's beautiful.
That said, the only apparent species capable of getting us off this rock and avoiding the total annihilation of all life are humans. If we die off and another intelligence emerges later on, all of the easily accessible energy for industrialization and getting us out of the gravity well may be gone. This is our one, best shot.
When our sun dies, none of this will have mattered at all. If we're still stuck on this earth, we may as well have never even existed. A brief brilliant flash that led to nothing and was forgotten.
The existential counter to that is if we can make it beyond our solar system. Maybe we evolve beyond our current biological forms, maybe computers become our custodians, who knows. Maybe some future super intellect revives all of the state leading up to it, and maybe we'll become (or already are) holographic simulations of what once was: memories of our world.
With respect to the geologic timescale and the fate of earth intelligence and biology, humans matter way more than orcas. That isn't to say we shouldn't go to great lengths to preserve orcas. But there's a much bigger story at play, and we shouldn't discount our place in it.