It's unfortunate that the headline and much of the article is needlessly sensationalized. Aggression can be the result of self-control, but it's pretty clear clear from the words of the researcher and the abstract of the paper that aggression resulting from a lack of self-control also exists ("We often fail to inhibit our worst, most aggressive impulses. But that is only one side of the story." and "balanced perspective, which allows aggression to arise from successful and unsuccessful self-control").
Research indicates that the brain’s prefrontal cortex, a center of self-control, shows increased activity during aggression, further debunking the association between poor self-control and aggression.
That doesn't debunk shit. It's obvious why the prefrontal cortex would be active in the case of premeditated aggression, but this finding makes perfect sense even in cases of spontaneous, uncontrolled aggression. In that case, the prefrontal cortex is trying to exert self-control, it's just failing at it. But that activity would still show up.
Very interesting findings, but the reporting is pretty poor.