Maybe so...but there are other avenues for this, namely informing the appropriate authorities first or, perhaps if you know the owners, notifying them.
Yes...some people are dirtbag pet owners. And possibly they'll take any such notifications about their dog(s) with less sincerity than they should. But responsible pet owners aren't that way. Certainly I know I take my role as a pet owner very seriously and the idea that my pet may have placed someone else in danger would not have me brushing it off lightly. The very fact that my pet was outside of my control in the first place would be a serious matter for me, even if he was the friendliest thing this side of Casper.
Like it or not...if you take such matters into your own hands, you may very well find yourself in court on the wrong side of the law.
If you can safely disengage...then do so.
100% agree