Pedestrian bridge, Auburn

A pedestrian overpass over the Western Motorway in Auburn.  There must be a couple of different gangs involved here, because each group has been crossing out the tags of the other.  

Note that most of these tags have been made with marker pen, not spray paint.

I imagine this is one tagger crossing out another - possibly as a warning to keep out of their territory?

Here, the other tagger takes revenge.  Note the cock on the right - that means the RTA has to clean this quickly, as the graffiti is offensive.  

A reminder of the exact location.

I've used the RTA "contact us" web page to report this, and told them that it is offensive.