3 (1) A Participant shall at all times act in the best interests of the game and shall not act in any manner which is improper or brings the game into disrepute or use any one, or a combination of, violent conduct, serious foul play, threatening, abusive,
indecent or insulting words or behaviour.
(2) In the event of any breach of Rule E 3(1) including a reference to any one or more of a person’s ethnic origin, colour, race, nationality, faith, gender, sexual orientation or disability (an “aggravating factor”),
I think that if you look at the charges against Suarez, it is perhaps wrong to get too hung up about whether the term 'Negrito' is abusive. Almost certainly by itself it is not (even if Evra didnt understand its meaning and thought it was). However the word would compound abusive behavior if it was used in addition under the rules because it would be a reference to the person's ethnic origin (just as calling Suarez 'Uruguayan' combined with 'abuse' would be an 'aggravating factor' as a reference to his nationality.) It is perhaps most obvious in the Terry case whereby the term 'black' is not abusive in itself but 'black c*nt' is 'abuse' with 'aggravating factor' of reference to his ethnic background.
If all there is to this, is that Suarez called him 'Negrito' then it is very difficult to pin the first charge of 'abusive behavior'. In fact, it is quite difficult to pin it anyway given that noone seems to have picked up on it outside of Evra. But if Suarez was being verbally abusive towards Evra in other ways, then I think that 'Negrito' (or even the use of the word 'French') would be considered an 'aggravating factor' that would subject Suarez to twice the normal punishment.
I would expect (or perhaps hope) the standard for proof of abusive behavior to be quite high - like for instance 'Rooney's swearing into the camera'.