There will always been offensive/racist remarks made on sporting fields and society in general - it's unrealistic to expect you can completely stamp it out and frankly some people need to take responsibility for their own sensitivity of being habitually offended, exaggerations or misinterpretations.
I mean I grew up and work in South West Sydney ffs lol
Not saying this relates to Erza not having a right to feel genuinely insulted and disappointed in this instance but Spencer doesn't need to be dragged too much over the coals for this either and has offered to apologise for something said heat of the moment.
Rule enforcement and compliance is not an effective motivator or behavioral modifier but I get why the NRL has to be seen to be making a stand and setting an example.
Punishment as a form of deterrent or post infringement justice does play a role and I also understand you can't just let people do what they want without consequences or society falls apart.
As an example a shitload of people still ignore the road rules and drive like numptys despite fines and loss of license/job ect. being a threat and alot of them are repeat offenders. It's human nature to straddle the line and discard restraint but the system of safety is based around rule compliance more than improving driver skills and culture.
Ofcourse there will always also be people that just don't know any better.