Jason Waller kindly pointed out, in a comment to this post, his discussion of a related topic, that is, whether it would not be better if our free will did not imply the possibility of doing evil. The idea is by Kurt Liebegott and Mikey Lorkowski, who propose that a juster God should have given us the possibility to choose between, e.g., donating 10 E or 100 E to a charity, but not between donating to a charity or stealing jewels.
You can read Jason's answers to Kurt Liebegott and Mikey Lorkowski's arguments here.
As for me, I would add that if we assume that we are not free, e.g., not to donate (although we are free to donate more or less and to the one or the other charity), than there is no merit in donating the minimum. We do it just because we have been programmed not to do otherwise. Similarly, I have no merit in the fact of never having destroyed a planet with a nuclear weapon, since I am just unable (because of external constraints) to do it.
More importantly, this "just God" would have made us in such a way that we could choose how much to love Him/Her, but not whether to love Her/Him or not. But can a lover rejoice because of a love the beloved one cannot help to reciprocate? If God wants to be freely loved, S/He cannot be satisfied with human beings who would never be able to stop loving Him/Her.
Now, a possible objection would run as follows: God leaves us free to love Her/Him or not, but not to do evil. But, from the point of view of Christian theology (which is what we are now testing), this is perhaps a non sequitur. We respect other beings because God's love enables us to see them as friends and not as enemies or rivals.
Thus, with the background of Christian theology, can ethics and God's love be separated?