Still just trying to get my head around where giving orders and taking action" is justification for someone being called a "fat f*ck" or ""dumb". As Squawk7700 mentioned, even the military doesn't pull that crap any more. When I was an instructor at RMC Duntroon in the early 90s there were still a few knuckle dragging Neanderthals on staff who couldn't quite grasp the fact that you don't get the best out of an individual regardless of gender by shouting and screaming abuse.
If the facts of the complaint were not true I doubt very much that the disgruntled trainee would have gone public. AsA have not denied those facts but even here there seems to be people who subscribe to this type of behaviour.
The trainee may well have not been up to standard but there are more than adequate provisions under the AQTF to deal with this.