You're neglecting many reasons extra terrestrial life may pose a threat.
The most obvious is they may want our planet, they want to live here, and if they've managed to travel across the vast void of space, wiping out humanity probably won't be particularly challenging for them.
Also, your second point is invalid, territorial reasons are not void. We may pose no threat now, however a technologically superior civilization may conclude we pose a future threat, and so wipe us out now before we can become one.
Also, the old 'dangerous biology from somewhere else!' is almost entirely null and void, organisms are adapted to their environment, they usually pose negligible risk to any other environment already inhabited by biological organisms. This is why, for instance we don't treat organisms from thermal vents as 'oh noes, biohazard material'.
The most obvious is they may want our planet, they want to live here, and if they've managed to travel across the vast void of space, wiping out humanity probably won't be particularly challenging for them.
Also, your second point is invalid, territorial reasons are not void. We may pose no threat now, however a technologically superior civilization may conclude we pose a future threat, and so wipe us out now before we can become one.
Also, the old 'dangerous biology from somewhere else!' is almost entirely null and void, organisms are adapted to their environment, they usually pose negligible risk to any other environment already inhabited by biological organisms. This is why, for instance we don't treat organisms from thermal vents as 'oh noes, biohazard material'.