Unless the gossip irresponsibly named a particular rival, I don't think speculating about rival colleagues is anymore "hateful" than speculating that the individual could be domestic help, or a tradesman who noticed a picture or googled a name.
The police have evidently DNA tested the immediate domestic help, and could be working their way through closely associated tradesmen, and then more distantly associated tradesmen (providing they can be identified). Rival colleagues are just as viable as suspects as tradesmen and domestic helpers and need the same DNA test .
SG has been out competing rivals over many years to arrive at the national level the same way NFL football players have.
As with NFL verse minor league football, the pay difference between major league, national level journalists and out competed minor league rivals who stayed at the local stations is likely vast. Likewise, the pay gap between a "starter" major league anchor and a "back up/ "second string"" anchor at the same station might be significant as well.
In the end, rival colleagues can have plenty of motivation in regards to jealousy and cash. Hoping I don't sound too shrill, but rival colleagues can make as good a pool of suspects as the pool guys. They just dress more stylish for work.