Humble Defector and Refocus
Your opponent would still gain control of Humble Defector.

I assume that by "after it is activated", you mean before the ability has resolved. After you activate Humble Defector's ability the second time, then there will be two instances of its ability on the stack, both targeting an opponent of yours.

When the second activation resolves, you draw two cards and you give control of the card to the previously chosen opponent.

Then, the first activation resolves. Even though your opponent has control of Humble Defector, you still control the ability that's resolving, so you draw two more cards you give control of the card to the previously chosen opponent (if it's a different opponent than the one that currently controls it).

Even if the effect were written along the lines of "Opponent of your choice gains control of Humble Defector", it would still end up under the control of an opponent since you control both abilities.