You don't know what they want. If you deploy teargas before any of that has happened then perhaps the behavior you object to was in response to escalatory behavior of yours. You're essentially saying you have the right to deploy force because it's justified by any subsequent retaliation. If people don't retaliate or take any defensive action then you can declare a great victory and say they wanted to but you dominated them.

Your entire chain of reasoning is built on the claim that you have special knowledge of the future. Fine, so do I. If these people are not stopped then they're going to build Skynet and there will be nuclear strikes followed by terminator robots. Prove me wrong.