a) Crichton did what he did as a last resort. He certainly didn't want to do it. He spent a good deal of time trying to find other options.
b) Giving wormhole weapons to everybody is just as big a risk without actually demonstrating what they could do. Nobody knew that a wormhole weapon would create a black hole that would swallow the galaxy, and nobody COULD know until Crichton demonstrated it. We don't use WMDs today because we have witnessed what they can actually do and we know that a nuclear war will likely mean the end of us all. You really think Emperor Staleek would have just taken Crichton's word that he shouldn't use the wormhole weapon? Hell no! He would have used it on the Peacekeepers the first chance he got, and he certainly wouldn't have the power to stop it.
I really think you're twisting the situation to fit your own views. Crichton certainly wasn't the one who decided that nobody should wield wormhole weapons. He was just trying to enforce what the Ancients told him.