They kill warlocks. Even Morgan didn't just up and execute Dresden when he suspected he was murdering folks with magic. He waited for the council's judgment and tried to get evidence or catch him in the act. If Morgan could do whatever he liked and make a report later or not, Dresden would've been dead in Storm Front.
I think you're confusing the average talent's fear of the Wardens with how they actually operate.
When Harry tried to bring in Molly for trial the merlins reaction to was something like "why did you not kill her yet" and "you are wasting time". Even with a warden they do not really trust like Harry the overview is minimal.
I am sure a lot of wardens do their jobs as expected but there is a lot of room for abusing power, cutting corners, acting on tunnel vision, ....
And little chance of discovery. In such an organisation you need only a few bad apples to get a reputation among people who do not dare to complain because there is no independent complains department and wardens will cover each other. Because that is what members of closed organisations do if they get the chance.
And if a bad apple is in a position of influence others will copy his behaviour because they think it is normal.
Wardens have power. People behave differently around them which makes them less aware what is going on.
And most importantly pressure to get results can do the rest. The whole structure promotes abuse of power and no real brakes on it. The only brakes are the wardens own consciences. That is not enough.
So I do not think they will all the run out to kill the kids but if one does there is little to stop him and other abuse will even be more likely.
