That's the interesting paradox of technological development. If it's out of the bag, then it's out of bag, but that cuts both ways. You can never control who will gain access to advancements. Even if you trust the custodians now, you don't know who they will be in the future, &c. Eventually you end up at a fork: either pursue and endless technological arms race or find some way to build lasting cooperative and peaceful relationships. As they say, the surest way to destroy your enemy is to make them your friend. Still a massive challenge, but presumably that's why empires eventually always fail. They don't know how to make friends.

There are no warrior cultures in space.

> As they say, the surest way to destroy your enemy is to make them your friend.

Defeat, not destroy. The best way to defeat an enemy is to make them your friend. Destroying someone would not be very friendly (unless they want to be destroyed).

You cannot control, but you can backdoor