You must look deeper. The Little Goons are not outraged. They are scared. This killing will expose Tiller for what he was. The Little Goons fear losing the moral high ground (which they don't have in any realm but their own twisted minds anyway). The Little Goons are panicking over the thought of normal folks not agreeing with them. They are pissing their pants right now over the thought of the majority of folks who don't give a damn that a bloody baby butcher met his maker today.
The idea of people being faced with Tiller's legacy, and then understanding the man held little tiny living babies in his hands and then murdered them in cold blood (with the blessing of the state), has the Little Goons in an emotional uproar. They don't know what to do or think. Right now they are in default mode: Outrage.
Outrage is a veneer the Little Goons often use to cover their insecurity. It's dishonest and, frankly, sickening. It is very damaging to their cause at this particular time, and they know it, but they don't know any other way to deal with it.