I was born in 1959 (my username is a giveaway) and had similar experiences to you of racism in popular culture. I also remember the terms of insult and abuse used by kids that referred to disability or colour or race, and most of it at that age as unthinking. 'Gypo' was used like 'spaz' and like 'dirty arab' and 'mong' and dozens of other terms - often to other able-bodies white kids in the same gang .
I remember seeing on the news if not first hand the landlord signs saying 'No blacks, no Irish, no dogs'. I also grew up knowing that white jews and white gypsies (many physically indistinguishable from their white neighbours) were mass murdered in Nazi death camps because they were jews or gypsies.
When I started working for Sheffield Housing Department in the mid 1980s I had to deal with cases of racial harassment and abuse on estates - first as a patch officer and later as a senior manager responsible for policies, procedures and staff training. Traveller families were definitely seen by many of their neighbours as a distinct ethnic minority and in some cases victimised because of that. They were white and with 'English' names, but they stood out and sometimes were assaulted or verbally abused (or their homes vandalised) because of it. The stereotyping of travellers as theives and 'white trash' was common - and often by people who would never abuse other groups on grounds of race or ethnicity or nationality. For some reason they saw gypsies and travellers as fair game. There is some of that attitude on this board too (and much more on another board many of us also visit!). I have always hated and been embarrassed by the 'gypo' chanting at matches.
I agree that in the scheme of things Joe Marler racially abusing Samson Lee, and Lee accepting the apology, is a minor incident if only it hadn't been picked up on the referee's mike. It was heard and discussed by millions of people though. Even if Lee agrees that it was just 'banter' (soon to evolve into 'high jinks' territory?) that was not the view of millions of viewers or of traveller groups. I think Six Nations Rugby bottled it (and bowed again to England pressure) and set a lousy precedent.
On a lighter note I hope there is some sympathy for those (few) of us who seem to be on the same side of an argument as Croesy. It is a strange and unsettling experience. In return I will give my sympathies to those (many) of you who are in the same camp as Goslow!