There's two types of people in the universe.
1. When they see a identical duplicate of themselves they want to kill it.
2. When they see a identical duplicate of themselves they want to frakk it.
Yes, yes, Will didn't seem to frakk or kill Tom, but what you're forgetting is that his stomach was already turned from killing a duplicate in up the long ladder and chose to steer Deanna's vagina at his doppelgänger instead.
Picard killed himself in Time Squared, and Shinzon tried to Kill Picard in the final awful movie.
These examples go on forever.
Animals have a fight or flight instinct, and civilized beings have a fight or fuck instinct.
God bless the world.