All you have to do is look at the political and business elite today to know that power corrupts. They will simply steamroll people who disagree with their agenda, no matter how noble they may think those agendas are.
Umm.. Politics and god like powers are a wee bit different. For one thing, politics are streamrolling over their own elected members for outright acknowledging their agendas
. I don't think that's a good comparison.
People will use even the slightest advantage to try to force their moral perspective on others.
If I had the power of a God, I could easily see myself forcing the world into a mold that I thought was best. I can't imagine too many people who wouldn't.
Picard's perspective in the episode is that one-day mankind as a whole will evolve to the same level of existence as the Q or perhaps higher. As they do so, they'll leave behind many of the uglier traits of the species. But they'll do it together and they'll learn how to exist in that world, together.
Giving one person God-like powers would be disastrous for the rest of the human race. No matter how well intentioned that person may be.