The term's first introduction to the UK was when Suarez was misquoted as saying it to Evra. He in fact said 'Negro' in an aggressive manner to a black man. They do use it as a term of endearment and it doesn't sit too well with me when its used to describe a black man in a friendly way. However its also used as a term of endearment for a man with darker features, i.e a white man with black hair and brown eyes. Are we now to understand that this white man with black hair's nickname, which he has had for his whole life, which he calls his son, is racist? Context is of course important. In English itself context is important. Even the term 'black' can be misused.
No, again reiterating that this is not the argument. This isn't a black and white 'racist/not racist' argument. It is perfectly possible, and in this case the actual context, to say something as a non-racist person that can cause offence due to a racial context. The question isn't "Is person X racist?", but "Is what person X said appropriate?".
In this case, going to a country where racial discrimination is a more sensitive topic than his own, it wasn't an appropriate term to use. Did the club let him down? Probably? Do people actually think he's racist? No - it's never been stated.
Is it appropriate to use the term "negrito" in the UK/Europe? No, as has been demonstrated. You can see why, as 'allowing' a word that is highly likely to be used offensively would be giving a 'loophole' to actual racists who are misusing social media as it is.
As has been noted, it's a failing on the club to have briefed or anticipated such an issue ahead of time, and surely a cultural 'expert' could have seen it coming. My original point is that his father trying to say "it's not racist because we use it all the time" sounds like excuses people made in the 70's for various colloquial terms for skin colours, takeaways, and nationalities. Similarly, people using those terms were just using 'socially acceptable' phrases, but it wouldn't be okay for someone's who had been in a 40 year coma (using the 'acceptable culture out of its boundaries' example) to go to Spain and refer to people as 'darkie' or the myriad of terms that have filtered out of normal use due to their social insensitivity.
It would have been simpler to just have said "In my country it doesn't mean anything offensive, but I'm sorry if that's been lost in translation".